According to Techpowerup the 4870 is slightly better at 1680*1050 than the GTX260 over their test suite
http://www.techpowerup.com/reviews/P...dition/26.html
Obviously if you play particular games then look for reviews comparing those games, so for example the 4870 is better in crysis but the GTX260 wins in unreal tournament 3 from the same link above.
So for your monitor dead pixels are a bit of a luck of the draw thing, backlight bleed though should be covered by any decent review, though bleed is normal from poor build quality so Dell, Samsung, BenQ and Viewsonic should all be all right but best to find a review for a particular monitor that takes your fancy.