Underground Vs Mainstream

I think underground is more creative, people trying new shit.  Mainstream is all about sticking to a formula hoping to sell records, but sometimes a new wave starts in the underground, and then becomes the mainstream later.  What do you think is starting a wave in the underground right now that will be the mainstream sound later?  Do you like underground music in general, or do you prefer mainstream stuff that is on the radio?  What makes you pick one over the other?