Just wondering

Which poker site would you choose if you were only allowed to play on one site? Also why would you pick that site?

PokerStars for the variety and amount of traffic.

Same here, and I've never even tried another site and probably will not any time soon. As primarily an Omaha-8 player, I can almost always find the game I'm looking for on PokerStars with either no or a minimal wait, while I doubt that would be true of most of the other sites. Not only that, but this site is well known to have by far the most donks playing on it. This can be good and bad, but mostly good if you're patient enough to wade through them and don't get too upset with the bad beats they will inevitably put on you.

The only real thing I miss at PokerStars is the lack of bounty tourneys... and, the fact that you have to get into the mid-level buy-ins to get into a deep stack tourney. Other than that... everthing else is top-notch... including their support.