i5 would game a bit better, FX would render a bit better. They're pretty equal overall. The FX could overclock a little possibly pushing it past the i5, but you really need a 990FX motherboard to get the best out of your FX.
what about the possibility for future replacements ? I know that the next gen AMD CPU 's will keep the AM3+ design.
Will the next intel keep the 1150 slot ? In other words, it's about the mobo compatibility.