Beyond accuracy, you want a paintball that will rarely break in your gun but will usually break on your target. In the last few years, many manufacturers have created recipes for high-quality paintballs but if you test a brand of paint and experience a lot of bounces, it may be time to try something new.
As a general rule, the more you spend on paint, the better quality it is, though I have seen cheaper paint that works really well. Ideally, you should experiment with several different brands and find the best paintballs for your budget.
One other thing to keep in mind is that different brands of paint shoot differently in different paintball guns. For example, some guns can shoot practice paint perfectly while others really need some high-end paint if they want to be consistently accurate. Additionally, different batches of paint from the same company sometimes perform differently, so finding the perfect paint can sometimes depend more on chance than anything else.