Which is better Pandora 或者 iHeart Radio?

I've never had any kind of satalite radio but I want to know which is better and why. My 老友记 say that Pandora but I like all the stuff that I've been hearing about iHeart Radio. So my 问题 is:
1.) Which is better and why?
2.) What's the difference between the two?
Thanx!