Which one should I buy considering I am never going to be playing high powered games like some of you.
Why buy something you don't plan on using?
As for which is better, that's the age old question when it comes to ATI and nVidia, since the answer changes depending on a product launch. I guess at this very single point in time, nVidia has a faster platform for SLI, since they offer a dual-GPU card in the 7950 GX2, which can be run in SLI, effectively offering 4 GPUs of rendering power. From an energy savings standpoint, ATI's XF chipsets are more efficient than Nforce5.