The ones from wallmart are ok, but since both pods stick straight down from the belt, they can sometimes interfere with your ability to cram into small spaces (especially in recball). I have a harness with shoulder straps, and a belt that clips around my midsection, I find this better for recball, as it sticks to my body and doesn't protrude much.
As for volume, if you play 4 on 4 or 5 on 5, 2 100 rd pods are plenty, but as you start playing bigger and bigger games, youll need more and more paint. But for small recball games, until you get really experienced and want to step up your game, the packs from wally world are fine.