clock for clock the intel is the better cpu. pair it with a 7870 and your on to a winner.
in benches there pretty close but thats because the fx had to use 6 cores to do the work 4 cores from intel do.
so over all the intel cpu is more effective. runs at lower volts so is cheaper to run and will save you money every day.
also remember that not every application will use 6 cores so most of the time your cpu will be 30% less effective than the intel especially in older games where single core performance is a priority.
there is much less of a chance of a gpu bottlenecking when a game only uses 1 thread on the intel over the fx.
but hey you pay your money and take your choice all i can do is give you an opinion... and that opinion is intel is currently the better option for the money.