The gtx 460 1gb is much better. in fact its so much better that the gtx 465 is already at end of life. if you overclock the 460 it will crush the 465 and depending on your overclock it will get you fairly near the gtx 470.
you will save power and have a lot less heat too if you run 2 X 460's. honestly thats the way I would go. The 465 is much hotter and much less power efficient. you will be much happier with the 460's. the only reason to go with the 465 is that you can run trip and quad sli.