They are both nice cards and you'd probably be happy with either one. A quick google search and benchmarks indicate the 5850 consistently beating the 465, but not by leaps and bounds. Keep in mind though that the GTX series cards in general are notoriously hot and power hungry when compared to the equivalent ati cards. Now I have been and always will be an Nvidia fan boy, but right now in terms of single card solutions ATI is where its at in terms of price/performance ratio. Another thing to consider is multi gpu scaling, say in a month or two you want more power and go to pick up another card to crossfire/sli (well SLI if you have a capable board, which if you have a newer amd board means no SLI for you). So assuming you're running an SLI capable system and were going to be getting another card for more power, many reviews I've read all show great scaling from both companies in terms of performance but again ATI has the edge. So considering those factors the 5850 is my recommendation.