7770 CF is faster but.
Crossfire creates more heat
Crossfire consumes more power
Crossfire has Microstuttering issues plus depending on what 7770 you are getting you may be bottlenecked by 1GB of memory.
Go for a 7870XT.
I totally agree.
*Raw frame rate numbers in benchmarks do NOT represent the entire gaming experience. It's far better to have a SMOOTHER experience at 40FPS then to get stuttering at 55FPS due to Crossfire.
The Powercolor got lots of reviews as it toggles between HD7870 and HD7950 depending on the game. However, looking at pricing it's $250 now which has gone up. You can get the Sapphire HD7950 for only $40 more after MIR so it's hard to recommend the Powercolor now (it's also noisier).
My advice is either get the best HD7870 2GB card for $230 or less, or spend a little more for a much better HD7950 like this Sapphire.