Whatever dump pouch you get, make sure it retains its mouth shape and is not floppy with the mouth folded closed and pointing downwards. Also make sure the pouch is deep enough and wide enough for your hands to dive into and not get snagged. If you’re using the dump pouch to retain mags, make sure the pouch is big enough for a couple of them. Also don’t get the mesh variety, they’ll eventually rip or catch an edge of a metal USGI mag.
The dump pouch may seem like an afterthought piece of equipment but don’t skimp on one. It’ll be the one thing that will cost you seconds in a match when it tangles up at the wrong time.