Tai Chi Push Hands and Wing Chun Sticky Hands:
As practiced in America, Tai Chi Push Hands is an exercise primarily designed to enhance a player's ability to remain balanced while in contact with an opponent. Push hands training improves one's ability to disrupt the balance of an opponent by "feeling" where his or her center of gravity is and exploiting it.
To protect one's own balance, a player attempts to diffuse incoming forces by sensing them and redirecting them. Typically, players begin facing each other with contact between hands and elbows and a simple pattern of circular movement. At some mutually expected point early into the movement, players begin to search for a way to disrupt the opponent's balance while maintaining their own balance through adjustments of position, stance, balance and hand position. When either of the players is "uprooted" or loses balance, the action stops and the players begin again with mutual contact and cooperative movement to start the cycle again. Emphasis is placed on using proper "technique" as opposed to "brute force" to accomplish this task.
Wing Chun sticky hands is an exercise primarily designed to enhance a player's ability to attack an opponent with, and protect oneself from open handed strikes, punches, elbows, knees, kicks, grabs, locks, etc. Sticky hands training begins with players facing each other with arms in contact and a simple "rolling" pattern of movement. At some expected time early on in the "rolling" players begin to exploit each other's position and movement with sharp, explosive attacks. Pulls, pushes, strikes and grabs are all part of the exercise. When one player manages to create a situation where he has "trapped" the other's arms and can land clean strikes of his own, play pauses momentarily to reset and begin "rolling" again.
There are many similarities between these two activities. They are both initiated from contact with the opponent. They are both started with a "cooperative" and predictable pattern of cyclical movement. They are both concerned with disrupting the opponent's balance by attacking his or her center of gravity. They are both learned in stages, moving from predetermined, cooperative patterns of movement at first, to freestyle competitive play at the advanced stages. Both exercises emphasis the use of "sensitivity" and technique over brute force. These training methods are quite similar in many respects.
The differences between push hands and sticky hands have to do with intent. The intent of push hands training is to teach a T'ai Chi player to "stick" to the opponent's limbs and body. While sticking to the opponent, the T'ai Chi player attempts to push, trip or throw. Striking is not the main emphasis in push hands training. The intent of Wing Chun sticky hands training is to strike the opponent while not being struck back. The T'ai Chi player will tend to stick to the limbs of an opponent wherever they go, while the Wing Chun player will "chase the body, not the hands" The T'ai Chi player will move in circular, flowing patterns while the Wing Chun player will use straight, jolting choppy movements. The differences between these activities are many.
The philosophical underpinnings of each style dictate the training methods used to develop martial skills. Wing Chun is primarily a striking art. Its methods deal with cultivating devastating striking ability and defense against strikes. T'ai Chi is an art mainly concerned with throws, pushing, pulling and locking. Striking is a major aspect of T'ai Chi fighting theory, but not as a part of push hands training. Also, Wing Chun is aimed at striking many times in a short time frame. T'ai Chi seems to favor more committed, single attacks of various types.
Wing Chun and T'ai Chi provide different paths to the top of the mountain. Whichever way you decide to go, enjoy the journey. Make sure to take your time and examine every last detail. Kung fu of any type can provide a lifetime of learning.