Its so crucial to take different things into consideration when trying to calculate your "win rate"
Rakeback / Races & Bonuses - Just because one room offers you X% rakeback, it doesn't mean that it is better than another room. For example on PokerStrategy Ongame rake races there are not so many places and it is relatively easy to get a good position on the rake board
Amount of tables available - Some sites, such as Bodog only allow you to play 4 tables. Other sites such as PKR have such amazing graphics that it is pretty hard to play alot of tables. Some sites such as Microgaming/Ongame/Full Tilt and PokerStars have really good software where you are able to play almost as many tables as you like. Obviously if you winrate is $x per table, if you can play more tables your overall winrate will increase
Volume of traffic - Ok cool, we have found a site that lets us play 1000 tables at once. Ship the two 50" monitors so I can crush some noobs. Oh whats that? There is only 5 tables running?
Standard of competition - If you could play 5 tables against the biggest fish in the world or 16 tables against the biggest nits in the world it is likely your winrate will be better on the "5 tables vs fish" than the big grind against the regs.
It's super important you take everything into account and don't just see some shady affiliate offering an illegal rakeback deal (that might not be there forever anyway) and put all your roll on that website. Be professional, do some research, find the right site for YOU and go win as much money as possible.