Bad question. Both are good in their own way. Why do you need the graphics card? Gaming? 3D work? What?
Then better wait for Fermi to launch. It should reduce the price of ATI 5850 and then get whichever performs better. You can wait right?
Don't go for GTX 275. It is not a Direct X 11 card, its a Direct X 10 card and performs marginally better than ATI 4890 which is priced at 12k.
So the 14k price tag is not justified, at least now when the Direc tX 11 cards are emerging.
My suggestion is waiting 1/2 months for the price drop in Dx 11 cards and go for the ATI HD5850 instead. It is far better than any of the present Direct X 10cards. It performs better than the mighty GTX285, most powerful single GPU offering from Nvidia.
today I gone to computer dealer shop in Nehru Place,New Delhi to buy HD5850....but there is not even one HD5850 graphics card available in the market....