Which video card would work better, an ATI Radeon HD 4870 CF or an ATI Radeon HD 5770 CF?

Im looking into a new video card and I need one that is beastly (run crysis fairly smoothly). This is mainly for all the newer games because my old card is, well old, but also partially for older games such as crysis, even though it can still barely be played. Also, would you have any suggestions?