5850 has more than just an edge, it is easily the faster card. I would take the 5850. however, if you wanted to add a second vid card later for xfire/sli, the gtx460 is faster for dual card setup. even a standard 5850 is faster than the 460 top edition http://www.hardocp.com/article/2010/10/18/asus_engtx460_top_1gb_video_card_review/6
The HD5850 is definitely faster and can OC a ton but both of those cards are over $200 and it would make more sense to spend slightly more on either a GTX 560 Ti or an HD6950.