come on now, we need more info than that. please list the exact cards you are talking about. also list all your specs including the resolution you want to play at and your power supply.
Raw speed the 512mb one will be faster memory but less.
Get the 1GB GDDR3 if you plan on using AA or going up the resolution to HD. gl
None of that is relevant. I am trying to discover if there is a reason I should take ddr5 over ddr3 when you have half the memory. If resolution matters then you tell me why, what I desire is irrelevant.