well i don't know what you mean by similar system; all sites are pretty much the same just look different
BUT there are some sites that are significantly better than others
stick to the big name ones: Fulltilt, PartyPoker
(though some would vouch against it), UltimateBet, and Pokerstars
, considered #1 by most.
do NOT deposit into pacific...it's one of the worst clients out there
edit: (i mean no offence by this, it's just a common thing that happens) most people who learn to play through play money usually develop bad habits that will KILL you in real money
so my suggestion is start off at a lower limit and work your way up...start lower than where you'd think you could play and feel it out