After running thru a strong comparison between ATI 6870 and GTX 470 I hv decided to go for ATI as GTX draws more power, is more noisy and hot too. However I am not able to see which make for ATI shall I go for from MSI, Saphire or XFX (which I think is little costly).
The 470 has much more overclockability. The 6870 is already clocked so high at stock that it really can't be raised more than 10% or so.
I would get the cheapest out of those 3 brands, but if you really feel that a double lifetime warranty is worth a little extra money, then XFX is the way to go.
+1.........I have a XFX HD6850 and honestly i bought XFX because of the Life time warranty so I'll always be covered if something was to go bad with the card not to mention their support is great and fast on the phone(had to call them twice about my serial number and registration).