Bench shirts add sophisticated strenght, taking the power that one already has and improving the preformance, stability and technique of the lift. Hard to explain if you have never used one (copout I know) but they can give mental, as well as a physical boost. In my view the mental part of lifting can be more important than the physical, at times.They also have suits for squating & and for DL'ing (not the same suit). Bench shirts could add a 50-100 to 200l+bs to ones lift, depending on the level of the lifter. Not usually worn doing regular workouts. Along with elbow & wrist wrap's, a customed lifting belt & shoes, a modern PL'er is set to go. In theory a lifting suit of any kind reduces injury. Of course that's in theory only.
Quite a few Raw meets have been developing of late. The lifting rules are not uniformed as yet for different contest. Though any Raw meet does not allow a suit of any kind as it's number rule. A few will OK a belt or wraps. A true Raw meet does not allow any type of add on's like a belt or wraps. For what it's worth,I favor a true Raw meet. Good Luck.