I guess like all things poker….”It depends” 
What kind of marketing you are going for and the type of people that will be drawn to your site.
I like Absolute Poker. The cover the whole spectrum pretty well. They have 40 freerolls a day, plentiful reload bonuses, great welcome bonuses along with WSOP qualifiers. Pretty standard T&C and never had a problem with them.
A lot of ways you can market AP and it is one of my better converting sites.
Couldn’t go wrong with any of the CAP Certified sites though.