NV's are slightly better, but ati's are very close (both VERY good overall except for nvs CUREENT drivers due to ENTIRELY new archetecture aka: they need some work on tweaking in farcry and overall perforamnce) I'm basing this over what I've read in the past on stability with games (John Carmack said something once about NV's being a little better also) and also what ive noticed in how much the 59XX series caught up to the 9800 series just through driver updates. (after the cheats were removed that is)
Secondly, it all depends on the game and also the rest of the hardware you are using. I mean just look at the numbers of say an nvidia chipset vs a via or sis chipset. You will notice that many nv chipset boards make it so the 5950 even does BETTER then the 9800XT. Y? Drivers, optimizations, other hardware, which card maker's card, etc. As anand stated, NV is prob going to be better for higher res and ATI for optimizing that res (AA+AS) = Both good cards in their own fashion and NEITHER sucking!
Based on what I said above, some of the differences between the sites may be due to this factor. Also, games arent all written the same. The numbers tend to flip flop on the diff games benched. Who knows how each card will perform on Doom3 and HL2 even. I bet if you used a P4 vs an A64 one card will beat the other card on one proc, where the other card had previously won. Same applies with game patches, and drivers (as mentioned above).
Thirdly, who cares?!?!?! What WE ALL NEEDED was ATI to release something within 5% of NV's top card OVERALL. What has it done?
1) the XT was released for benching earlier then expected
2) XT's speed was increased (20mhz core/100mem)
3) 6800U's speed was increased, but put into a new card cuz their Ultra was already officially released (50mhz).
4) They will probably release better drivers (NV already has one) and not delay their card's releases if given the choice.
5) This all causes prices to drop. (5900/9700/9800 series will drop in price due to 3454543 higher cards in the market)
6) BOTH companies will probably make money and stay in buisness against eachother (THE MOST IMPORTANT OF ALL FOR FUTURES SAKE)
Due to not knowing all of the variables mentioned way above, we might as well call these cards fairly equal in how fast they are at all types of games. (ex we dont know about how many optimizations each can make nor the true status of maturity of drivers, nor the hardware differences, etc, etc ,etc)
Finally, it all boils down to what u build. If you have such hardware as an FX or EE processor in your computer, a WD raptor hd, overclock above 3.5 gigs, or perhaps have a $1500+ custom build computer, then NV's TOP cards (6800U/6800UE) arent an issue with power sense i imagine a high psu is already in your system, or u have the resources to acquire one w/o hesitation. Think about it. Another point is that these people will already be willing to fork out an outrageous $500 for the card, therefore I imagine they will have the money to get the psu also. You will also get PS3.0 and FP32 out of the deal.
On the other hand, like most of us, you dont want to spend that much, and would settle for something more in the $250-$300 range (for sake of argument). You will NOT be buying the top NV card due to you not wanting to add a psu cost to your computer, and having ur current psu already (most likely) not being the best of psu's due to your non-compulsive tendancies to put 1/2 a grand into each component. ALSO you will not be buying the top ATI card, due to it being JUST as much (minus the cost of the new psu). It is already too much, so who cares about either of them!
Or there are people like me. These people are looking at the current, almost top-end cards taht are out now that cost ~$150-$200. We are the type that are looking to get that 2500+xp and oc it to 3200+ speeds and top it off w/ one of these cards. These people, as all three of these groups, MOST BENEFIT if the cards are very similar in performance. The prices of ALL of the cards (except the very top card at any given time) will drop in price. Who knows, maybe the 9800pro will be ~$120-$150 by mid-summer and these people can finally upgrade their GF3's.
You people get the point? Sorry for it not being more organized, and i knwo there are exceptions to these catagories of people, but most of all, I think 80% of people fall within these catagories or there abouts. The fact is, the benchmarks released today would have BEEN WORSE if ATI truely beat NV or vice versa. Just give it up, and try to educate people into thinking on what is actually the more important outcome of these releases and thank both companies for having archetecture that actually follows the direction of where the games are going (ex: no math/texture unit being in the wrong place like in NV30 w/ its long stupid pipeline that took forever to optimize the drivers for)