First I suggest you read the book Laughing and Crying by H. Plessner http://en.wikipedia.org/wiki/Helmuth_Plessner It is a phenomenological study of these two states.
Laughing and Crying are extreme opposites and thus the Buddha, as Buddha would not indulge in them voluntarily. The Buddha is portrayed either with no expression or slightly smiling. This is trying to portray serenity. The Buddha is serene because he has been released from the wheel of samsara and no longer is under the sway of Dukkha which is dissatisfaction. It is the kind of dissatisfaction that Tantalus has when he reaches for the apple from the branch and due to the action of the wind and the waves he is standing in he can never quite reach the apple. Basically nirvana is non-attachment to the things of this world. If you are not attached to this world then things come to you, while if you are attached they flee from you. Serenity is not taking notice when they come to you, and not going after them when they run from you. Non-attachment in this sense is called Wu Wei non-action in China. It does not mean not eating, or sleeping, etc., but it means doing nothing to excess, not holding on to things, and going with the flow of happenings rather than against that flow. Non-Attachment is something that is very difficult for humans to attain because of our dependent nature. Non-attachment does not mean preventing oneself from getting things or it does not mean getting rid of things. If it is an act of will against oneself (Asceticism) then it is not non-action. Preventing or forcing oneself is not non-action. It is instead freedom from the necessity of preventing or forcing oneself. That is why it is serenity. In Islam it is called Zudh: doing without. Zudh entails indifference to ones conditions, if one is in the shade one does not need to move into the sun, and if one is in the sun one does not need to move to the shade. One may move but oneself is not forcing oneself to move. Zudh entails giving back more than one owes, and taking less than one is owed. It means giving each thing a little more than it is due, and demanding less than one is due. It is not indifference. It is spontaneous action that supports other things in their needs, while not taking everything one needs oneself. This slight imbalance engenders the gift and eschews the idea that things are independent and self-supporting. Buddhism is looking toward perfect balance of indifference. Zuhd wants to be slightly out of that balance of indifference, because it wants to facilitate the giving and receiving of gifts. But in both cases there is an approximation to Taoist non-action. Taoist Non-Action is a certain orientation to what is going on outside oneself, where oneself offers no resistance to what is happening naturally and spontaneously. Buddhist non-action has to do with ones will and its relation to things in the world. Islamic Zhud is nondual between these two approaches. It wants lack of attachment and flow with the flux of the world, but it wants in the interplay between the two to engender an economy of gift exchange.
In Buddhism as it was originally envisioned it was solipsistic, these are called the Ahrats, who just wanted to achieve nirvana for themselves. Mahayana wants to perfect the teaching of the dharma by giving priority to compassion for others over oneself, so one seeks liberation for all others before oneself. But the tradeoff is that one expects to be fed though begging in order for one to lead an exemplary life of compassion that shows other the way by example. In Taoism the orientation is toward not leaving traces in the flow of outward things. If one learns to do that then one becomes transparent to other things offering no resistance what so ever. Taoists become hermits who live alone and support themselves off nature, and have restricted iterations with others. Now notice that there is a slight imbalance here where Taoist hermits seek independence and solitary existence, usually in the wilderness. They avoid transactions with others, but try to limit their transaction to those with nature. Stonehouse criticizes the Buddhist monks for their begging. Buddhist monks on the other hand set up a fundamental transaction with others on which they depend. They take their sustenance from others with humility, as a way toward their ascetic lifestyle. In return they pray for others, meditate, and help others, as well as attempt to save others from illusion. This means that they are constantly in contact with others through the transactions by which they get their sustenance unlike the Taoist monks.
Sufism within Islam has a different ideal. First of all there are no monks. Everyone is expected to marry and have children. One’s worship is on one’s own time, say in the middle of the night, when everyone else is asleep. During the day one is supposed to earn ones living and to support others in one’s family, close kin, neighbors, distant kin, and strangers. In other words one supports those who are closest to oneself first and others later and less that are more distant. In that support one is continuously giving gifts as one can afford to do it. Giving better than one has oneself to the other for the sake of God is the idea. Depending on God not others for one’s sustenance is preferred. God gives oneself gifts of sustenance, and one gives gifts of sustenance to others less well off than oneself. This gift economy is meant to eliminate the extremes of poverty and wealth. One is supposed to be spiritual in the context of having a wife/or husband and children. In other words in the midst of the chaos of life, rather than leaving home as the Buddhist does, or going out into nature to live alone as is the Taoist ideal.
Stonehouse who was both a Taoist and Zen Buddhist monk at the same time equally partaking in the Void and Emptiness with one in each hand, continuously describes the hell of illusion that exists in the villages and towns that he left. The ideal of Sufism is to live in that hell of illusion but to cling to both emptiness and void at the same time. One is clinging to void to the extent one gives more than one is expected to give. One clings to emptiness to the extent one expects less than one is owed. Zudh approximates non-action slightly imperfectly and for that is more perfect in as much as it engenders an economy of giving as part and parcel of the exercise of non-attachment in the midst of myriad possible attachments. It is expected that the Sufi will fail many times in this environment to live up to that ideal and for that he asks God for forgiveness.
Thus in Islam weeping is the preferred state for the one who aspires to the forgiveness of ones faults by God. So much is this the case that the Prophet advises pretending to weep if one cannot weep spontaneously. Because the nature of reality is one that should cause weeping. Existence is loss, no matter how much one gains temporarily. So the weeping Sufi is a more apt portrayal than the laughing or crying Buddha. In Islam one may laugh but not to the extent one shows ones teeth. One may cry and weep but not to the extent one tears ones clothes, and not interminably. In other words extremes of human emotion are limited but not as greatly as they are in Buddhism. In Taoism there is no idea of limiting extremes of human feeling so long as it is spontaneous and natural. Only fabricated emotions are to be avoided.
This is an example of how with respect to a central tenet of all three nondual ways that they have their own meaning for non-attachment. Ideally the Taoist takes his sustenance via direct transactions with nature, like Stonehouse does, except occasionally he sells firewood for money to buy supplies that he cannot produce himself. Ideally the Buddhist lives off of gifts of others that are not solicited, but given freely as others seek merit by supporting spiritual practice that they cannot do themselves. The Sufi within Islam is expected to hold down some sort of work and support others of ones immediate and distant family, and immediate neighbors and strangers. One is expected to engage in tall the transactions that could cause attachment in non-attachment, with the caveat that one is not expected to perfectly adhere to the correct behavior in every case, and that one is allowed lapses as long as one turns back to God as soon as one realizes one has gone astray. This imperfection of practice is supposed to underline the perfection of God and the fact that perfection is unobtainable by humans. This state when realized completely is called the perfection of perfection and imperfection. In other words, the asymmetry that underlines the perfection of god, in contrast to one’s own imperfection within the attempt to become more perfect, is a greater perfection than perfection itself at the lower level of abstraction. In other words dynamic perfection and imperfection is of a higher nature than static perfection and imperfection. Dynamic imperfection gives us the emptiness and void, as we expect less than we deserve, and we give more than is deserved by others. But this produces its complementary dynamic perfection which is more perfect though asymmetry in as much as it does not expect to arrive at complete perfection which is Gods possession alone. It assumes that whatever people do is going to be somehow or to some extent imperfect and as long as they ask for forgiveness from God for those faults then they will not have to bear the karmic consequences on the day of rising.
Buddhist search for Nirvana is a way of attempting to perfect human nature. Taoist following the Tao and attaining Te (Virtue) is again a vision of perfection of the human that offers no resistance to natural forces. Sufism does not attempt to attain perfection, but only to approximate it leaving perfection itself for God alone. But this assumed continuing imperfection generates an economy of gifts that circulates within society and thus stems the extremes of wealth and poverty in society.
Now it is hard to talk about this without considering the nature of the Indo-European worldview which is based on dynamic clinging and eschews static clinging. So notice that the emphasis is on clinging not on the lack of attachment as it is in the nondual ways. Baal was the god of covetousness, and Baal was essentially Zeus, the two faced god. Indo-Europeans have always spoken with forked tongue in order to get what they covet from others around the world, stripping them of their resources as thieves who engage in highway robbery around the world stealing what other societies and cultures have at gun point and justified by Manifest Destiny. The perfection of the Indo-European way is to attain dynamic clinging instead of static clinging. Dynamic clinging is when a parent lets their child leave home and do as they please when they are old enough, so that they will come back when they realize that home was not such a bad place after all, and their parents are only human. Static Clinging is when the parent does not allow the child to leave home, and so the child rebels and filial ties are broken. The perfection of this is seen in the best of rodeo riders who ride bucking broncos, and you can see that there is no stiffness in their bodies at all but that they flap with their body bowing as the horse bucks, and thus they cannot be dislodged. Static clinging is the cowboy who is stiff and tries to ride the bucking bronco as something separate from themselves, who try to dominate the horse even in its wildness. The nihilism is that the bucking bronco is bucking because it has been hurt within the confines of the stall before it is released. And so the nihilism is that the effect of the bucking of the bronco is artificially induced so that we can see if it is possible to ride it. Once horses were truly wild and had to be tamed to be used. But the practice of breaking horses has continued artificially as a sport that provides a spectacle due to its extremity of action and reaction between the horse and the human. So there is lust which is direct, but covetousness is indirect. And it is the indirect covetousness of Baal that is outlawed in the Ten Commandments.
The difference between dual and nondual ways are stark. We are surrounded by an addicted society, and the trick is to not become addicted so you can take advantage of others who fall into addiction. But everyone falls into different addictions, and thus goes to different extremes. Everyone does good in some respect, and evil in some other respect. As Dostoevsky says each person has a good and bad daemon who is another person. One person could be the bad daemon to one person and a good daemon to another person. The good daemon for anyone is trying to get them to do extreme actions in a negative direction, and the bad daemon is trying to get them to do extreme actions in a positive directions. But the daemons that we are to each other are all trying to elicit extreme actions that depart from the middle way. All nondual ways attempt to return to temperance. Sufis weep and laugh, but avoid uncontrolled crying and laughter. The Sufi does not attempt to become indifferent such that they face whatever occurs with perfect equanimity. Nor does the Sufi accept whatever overcomes them as just natural spontaneity. For instance, when one is angry one must sit down, and if that does not work, one must lay down. In other words one must avoid actions that follow from anger directly, that are likely to be irrational and regretted later. The relation of the nondual ways to each other, and to the Western worldview is subtle and interesting, full of wisdom. But this analysis of Zudh, just one Sufic ideal, shows the inherent relationship with emptiness and void subsumed within an overarching synopsis that is more difficult to realize because it is supposed to occur in the midst of everyday life in which monasticism is discouraged. However, if the Sufi comes upon a monastery he is required to leave it alone and not touch it nor bother its inhabitants. Thus the relation between Sufism and Buddhism or Taoism is one of being hands off leaving them to their Lord who knows what they strive for and what they attain better than any humans do.
The Buddha smiles, the Sufi weeps, the Taoist Laughs.