Variety is definately key particularly with Tournies.

Party: Has a lot of cheap ($6, $11) MTTs - but nice bog standard freezouts - usually about 550 players in the day time and about 1200 in the evenings. Also has plenty of freerolls if that's your thing. Nice loose players but not insane. - oh - and new players get a 1k freeroll in the 1st week and then 1 months worth of daily $250 freerolls

Full Tilt: Tighter players imho. Great bonus but I find the cheap tourney's practically non existent, and if they are there, then they are rebuy+addon which means they aint so cheap any more. Freerolls - forget it - everyone one listed seems to be private - think they are very mean with freerolls - unless they are buried so deep in menus I can't find them.

Only 2 I have experience with on your list.

If you want to play smaller field tournies then Cake is very quiet at the moment.