Just google anywhere, it tells you that the HD7870 is the old version of the new GPU = R9 270.. and i know the R9 270 is better than the R7 260x
Regardless of that website, i can personally tell you.. YES its better lol. I always use that website, in my opinion its just cold hard facts, look at the numbers (ignore the benchmarks if you want) its faster, more memory, more shader units etc etc