Frankly, Rollins promises more laughs, and that's apparently what most Americans have been reduced to longing for. Biafra, on the other hand, has more imperative political commentary to offer, but he's just not that much fun.
Both “spoken word” artists are worth seeing at least a couple of times before you reach your 40s, and I recommend Rollins over Biafra simply for the fact that Biafra's tirades tend to make you afraid that you're being followed home (which you just might be), and Rollins makes it seem sort of OK that you buy a lot of Pepsi and trust your government.