dspyrido wrote:There's subtle differences but it's not easy to explain so it's almost begging for ... why bother.
A lot of the differences (e.g., stepping, landing, sliding of back foot, dantian, spine, bows, flesh & bones, pulling, grabbing, etc.) have been explained by dspyrido, GrahamB, D_Glenn, etc. Although, some of the differences may be arguable.
dspyrido wrote:Coming back to the question:
What makes Bengquan different to a straight punch?
One difference that can be seen but can't be done on a punching back is the pull back motion of beng. It's a grab and pull back.
So far everyone here is taking about beng as punch to the body or something that helps train coordination. It's that but also has chinna baked in it.
When the lead arm grabs and pulls back the striking arm can also pass the opponents potentially extended elbow, impact it to jar it while on the way to the torso. There's many other subtle applications of beng like this.
This is not much of a difference, as the straight can be preceded by a jab or hand trap (pull down guard in boxing or MMA). MMA (an easier example to analyze fighting) has fighters/trainers with experience in Wing Chun, tai chi, etc. MMA does use trapping, hand fighting, grabbing, hand control, etc.
Many times a feint and hit using the opponent's momentum (e.g., walking in) is more effective (e.g., timing, efficient, avoid counters, distance, etc.) than a pull or grab. GrahamB posted a video with Paul talking about some of the problems with bengquan. Also, Trick's posted video showed the Xingyi player demo pulling and grabbing but did not use it in sparring.
The punching bag can be swung to create incoming force/momentum.