I have active accounts on 4 sites. The last one I added was FullTilt, in April this year, through
rakeback.com affiliate.
Through April and the first 2 weeks of May, my bankroll went almost straight down and I swore the site was rigged or at least something different was going on as I had never experienced anything quite like this. But, I had a 4 month plan to play on the site while I cleared the max sign up bonus, so I persisted.
I adjusted my game - upgraded may be a better word, and applied my new skills to not only FullTilt, but the other 3 sites as well. I am well into the positive on FullTilt now and feel I am a better player on all sites.
For me, it seems I will always lose some $ on one site each month and make money on 2 or 3 of the others but in the end I really don't see a difference in the way the cards fall on any site overall.