I am not much of an expert but if you want hardware comparisons then go to toms hardware and you will find more than you ever wished to know about graphics cards and every thing else hardware releated.
one of the main differences in the new Radeons compared to any other card out the at the moment is the new specialised hardware for doing Hierarchical Z buffering ,
this is for doing Occulusing Culling and reduces the fill rate considerably.
that is if you where rendering a large scene where lots of objects blocking one another from the viewer point of view then these cards will kick ass. ie High depth complex scenes ..