Im playing in both sites.
Like the software very much on both, can play games i want in both, cashouts are fast in both, play level is pretty much the same in each one (for my games level of course), Fulltilt have big fee in micro private games, but Stars also have bigger fee in $3 S&G games, so are close.
Minimum cashout in Fulltilt is $50, min. in Stars is $10, costumer service is good in both.
I think is where you feel more confortable, so far both are ok for me, get same amount of bad beats in both too.