Image quality is identical. the 5770 will be about 10-15% faster on stock clocks. It depends entrely on what you are doing, but unless you are playing games like STALKER, Crysis, etc. or overclocking heavily, the 5750 is a better value.
That is with both at MSRP though. If they are within $20, get the 5770 for gaming.
A forum community dedicated to overclocking enthusiasts and testing the limits of computing. Come join the discussion about computing, builds, collections, displays, models, styles, scales, specifications, reviews, accessories, classifieds, and more!