I do love both but i'd have to go for Stars for me.
The lobby looks alot more better, and its easier to use.
There MTT's are allways jam packed (more $$$) and the SnG's have great struct. Altho i'm playin NL10, the cash games are filled with fish (more $$$).
I would love to have Supernova status but thats gonna wait. The rewards for b-in Supernova are amazing. Stars are also bringin out there SCOOP event which have buy-in's for all levels. Im going to sat into a few of the bigger ones (would love a $10,300 ME tix).
I think there software is smoother (less crashes/freezes) and I do like there backgrounds better than Full Tilts vegas/beach/space or midnight backgrounds. Full Tilts avatars are good but there gettin a bit old and they should bring out some new ones.
Both are great sites at the end of the day with lots of traffic n lots of fishies, but i'm picking Stars as my online home atm