Remember the 295 is faster by at most a small margin and the OP asked for "best", and max FPS is not everything.
The 5870 is a single GPU, is DX11 ready so is future proof, requires less power, is quieter, is for the most part cheaper and as someone above has said has better minimum fps. It also has more connection options.
The 295 is DX10, is dual GPU, runs very hot, requires a small coal fire power station to run it, is louder and is nearly as hard to get hold of as the 5870, the only 295 OC have is over £400 which is an absurd price to pay for it.
Eyefinity is specialist, people shouldn't quote it as a reason to by as 95% of people won't ever use it.
Now I won't deny the 295 is a stonkingly fast card, but it basically comes down to this, do you want to sacrifice future compatibility and newer tech which remember with drivers can only get better, simply for 5 FPS and any problems dual GPUs may have? if yes then feel free to go back to banging two bricks together because you are obviousely easily amused.