I've owned both cards and theres no comparison between them, the 280 is hands down better. The extra RAM also has the advantage of quicker loading times and a overall smoother experience.
You forgot to add a bit to make what you're saying totally correct!. (At 2560x1600 and ridiculous amounts of AA like 32xAA) Which most people won't use or even feel the need to do so.
So to that point it's your scenario that it's not suited for. Your needs from a card are really not what the majority needs and I think that's what I've been disliking about your reports. The GTX 260/280 was built for your needs just as the X2 4870 was (bandwidth monsters). The other cards (4850/70) will not cope with the amount of AA you require and at that resolution, for most they won't have this problem. You need to start making this clear when you post about this subject. When you have done, many people have replied that they would not need the amount of AA that you prefer.
Yeah, damn them for developing PhysX support for my 21 month old card.
Physx is useless right now though. Wow, UT3 which isn't really that popular and Vantage have the main use for now. Oh and those who play GRAW2 still.
One benchmark that means absolutely nothing to a gamer and two titles that most have played or have moved on from by now.
If Physx was mainstream and it was in most of our gaming then I think you have a point. The fact is that it's not, just like Quad Core isn't needed for gaming yet, or like the launch of DX10.1 to give ATI cards mandatory 4xAA. At least ATI's feature will give something that just about everyone will want. Physx is a miss for most.
By the time it is mainstream then both AMD and Nvidia will have the capabilities to do so. CUDA runs the Ageia Physx engine right now so they can only get better so might have the better performing cards come the time for AMD to come to the market with their solution. Havok and AMD look to be working on something so time will tell. Physx for now is useless. People that promote their new Vantage scores well, they are really just clutching at straws.
You know performance on the 9 and 8 series and improved allot since the launch of the GTX series, think I gained over 1000pts in the vantage GPU test on my old 8800GTX in the last month alone....Damn nvidia indeed.
C'mon Shocky. You think a benchmark improvement is a great thing?. I've got the Physx driver on and Warmonger was erm good for to see it worked then taken off my system. UT3 I'm done with for now and it might help me in GRAW2 if I get around to playing it. The fact is, that it's about as useful as a Quad core CPU in gaming (except Sup Commander, and a slight boost in UT3).
I don't deny that it's a great free addition for old hardware. I think it's marvellous. It's just not useful for now where as if developers implemented DX10.1 there could be a significant boost in all games for ATI and I think that is more useful than Physx right now. Really, it's all pretty useless right now as it's not mainstream. By the time it is mainstream, both will be ready.
http://www.custompc.co.uk/news/602763/amd-announces-physics-partnership-with-havok.html
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Sorry about that Brammo

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If you're crazy about AA and would love nothing more than to pump this up whilst gaming then I think it's down to two choices for you. I wouldn't go SLI with the GTX 260s. I think it's down to the GTX 280 and X2 4870. In this situation and at your resolution I would go for the GTX 280 easily.
The X2 4870 is still seeing gains at 4Ghz so there could be more to be released from this card and as MR.B has stated the X2 4870 and GTX 280 cut it no problem at his resolution of 2560x1600 and he is below 4Ghz. So I think the X2 4870 would be slightly wasted at 1900x1200 if it's running MR.B's resolution fine and there could be more with increased CPU speed The much cheaper GTX 280 will be efficient enough for your gaming needs.
If you went for the single 4870 and in some titles the amount of AA you required @ 1920x1200 wasn't giving you performance you wanted then I think the extra £70 would be a good investment. I do think that the 4870 on it's own would be enough but because you were willing to buy two GTX 260s then it's seems sensible to me to get the fastest card that will be ready to handle the Vram limitation that you
might address with the single 4870.
If you would rather save the money then you could always have your PC ready and then just buy the 4870, test your gaming out over a range of titles and if you think you've made the right choice then just be happy with your purchase. If however you feel as if you could do with a little more grunt then you could send it back and get the GTX 280 as long as you do it within the first week. I think in your case you have a good reason to have the ability to do this so you don't make the wrong choice.