ATI cards tend to bench very well compared to nvidia cards; I'm not entirely sure whether that's due to nvidia being in bed with the game manufacturers and artificially inflating their game performance, or if the nvidia cards are just more gaming oriented. Either way, benchmarks aren't the end all.
On the flip side, any of these new cards can handle pretty much anything any game has to offer (hopefully including the new crysis sequel, assuming they find a way to make it run more efficiently,) so really I'd almost rather have the card that benches higher. Isn't e-peen the whole point of $4k setups anyway?
To be honest, at the moment i don't see any reason to upgrade. Nehalem looks VERY promising, but I really don't need it yet. I figure that I've had my couple months near the top of the heap; I can't afford to stay on top ALL the time. I'm holding out until Sandy Bridge on processors, and waiting for the next BIG jump in gpus (ie nvidia 8600 -> nvidia 8800)
But hey, if you got the cash... crossfire seems to scale better than sli as far as i can tell, so I'd definitely go for a pair of 4870x2 cards. I'm sure they'll be significantly less expensive than whatever dual cards nvidia throws together. Watercooling the dual ATI cards is easier as well. And if you can afford these cards, you can afford water!