2xgtx 460 1gb vs hd 6950 2gb

Better for what?
Performance? Noise? Heat? Cost? Hassle-free? Drivers?

better overall excluding the cost

Performance: 460 SLI
Noise: 6950
Heat: 6950 (Cooler)
Hassle-free: 6950
Overall: you decide

Upgradebility: 6950 (since you could crossfire it in the future)

I myself went for SLI GTX 460 cause I had money to buy only one card, then I added the other one months later.

I have EVGA GTX 460's SLI'ed. O/C 840/1680/2000 no voltage increase.
Unigine Heaven 2.5 Score 1945, 77.2 FPS, 40/180.8
Stock single GTX 460 830 Score 33FPS, 19.1/17.1 min/max.
3D Mark 11 SLI O/Ced w/ I5 2500K @4.2GHz 7409 3D Marks 7791 Graphics.
Idle 37C, highest 57C w/ side panel fan which lowered my load temps 10C.
No BF3 bench. Maybe when I can get it for $20.