Which is the Better Customizable Internet Radio: Pandora or Last.fm?

I’ve been playing around with customizable internet radio sites the past few days, specifically with Pandora and Last.fm, but I can’t decide which one I like better.  Both have their pluses and minuses.  Overall I find Pandora a bit cumbersome and often missing some of the artists I’d like to listen to, but it doesn’t just play the artists that I ask it to (which can be good and bad).  What I like about Last.fm is that it is more than a radio site, in fact the radio function is just one feature.  It also has tons of artists, especially ones on very small labels and that I like a lot, but I’ve noticed that some songs seem to get repeated more than others and that is a bit frustrating. 

I’m relatively new to using these types of services/sites so I’d like to get some opinions from those who have more experience with them.  What is your favorite customizable internet radio site and why? 

And if anyone out there is at all curious you can listen to my stations on Pandora and Last.fm here and here.