I would go for the ddr5, some games wont take advantage of dual graphics, DX9 in particular. In that case it will use the faster video card, if you have your monitor plug into the discrete video card it will use it, I know some motherboards ask you to plug the monitor on the onboard video when doing dual graphics, but you can always plug it to the discrete one and see if it works. If it works it will use ddr5 not 3. Plus what's the difference in price for the ddr5 vs ddr3? if its not much ddr5 is much better.