The performance of the GTX 465 falls between the cut down GTX 460 and the full GTX 460. Its based on the older and larger GF100 GPU, which is the same as the GTX 470 and GTX 480. While this might sound like good news it does mean it uses a fair bit more power than the GTX 460. Also, the GTX 465, 470 and 480 are based on yields and the 465 gets what is left after the two more powerful cards in the series have taken all the best GPUs. The lower rated GPU is then hobbled so that it can only use 11 of the 16 SMs (streaming microprocessors) while it's bigger brothers use 14 and 15 respectively. The biggest problem with this GPU is the sheer size of it, those 3 billion transistors burn an awful lot of power and put it out as heat.

If you can pick up a GTX 465 at an appreciably cheaper price than a GTX 460 then go for it but I would personally still prefer the GTX 460 as it is a better card.