+1 for Outslayer. If you're going to go the water bag route, I'd buy a round buoy to use as a body snatcher. But if you had to pick one, I'd go with the Outslayer bag.
I used to have a 140lb. Ringside water bag which was fun to hit, but after a few years it deteriorated (partly because it was hanging out in the hot Californian sun) and had to be tossed. I've considered getting another one, but have not found sufficient reason to do so—I'm fairly satisfied with the Outslayer.