First, PaddyPowerPoker is now part of the IPoker Network which does not allow US players.
Second, I am a UK player but have actually found that sites who accept US players to be tougher! However, from what I have read and experienced myself, it seems that good players gravitate towards Full Tilt,
poker stars and Ultimate Bet.
This suggests that you should head towards Bodog or Absolute Poker for the soft competition.
*You can ignore the next bit but for my own experience of these sites see below*
With Poker Stars, I deposited $100, got overconfident and then lost it fast on high limits. I then deposited another $100, got it up to about $150, dropped to around $120 - and then got frustrated and tilted it all away in 30 minutes on the $5/$10 tables. (
bankroll Management was not something I took seriously then.)
With Ultimate Bet, I deposited $400 solely to build up a bankroll through their bonus system (which is one of the few that don't expire within 1-3 months or so.) After 3-4 months OF A HARD SLOG on the low-limit tables I had got up to $500. (That's $100 profit after a slow grind through the low-limit tables.) With about $290 still to work off I decided I'd had enough and so got out of dodge and cashed out. In other words I found UB to be very tight indeed.
Absolute Poker was a breeze when their sign-up bonus system gave you dollars when you didn't require to see the flop. Got my $200 deposit right up to $400 fast. As soon as they changed their conditions I kinda got resentful and played badly - and this brought my bankroll back down to $200 before I cashed it out.
If I was to go back, I'd sign up with Absolute for the softness of competition though.