The only downside to either, it seems, is that they are out of stock - at least at Bud's.
This is just me, but I have never understood the reasoning behind folks who want to scrunch up on a shotgun stock that is way too short for them by getting a youth stock. I do not want my thumb to be recoiling into my nose with such a short stock. I realize a lot of new folks 'main exposure was to a M4 with shirt stock, but in action games where either you or the target is moving, you want to point the gun and that means it has to fit.
As to the functionality of either - one has a larger mag capacity, the other a short stock, otherwise they are the same gun