Intel sandy bridge chips (i3/i5/i7) outperform AMD phenom II chips due to better architecture and more instructions per clock cycle. This is why a core i3 2120 (dual core) at 3.3ghz outperforms an AMD Phenom II 965 (quad core) at 3.4ghz. The only upside of AMD Phenom II chips is that they can be overclocked whereas the core i3 lineup of CPUs cannot. If overclocked enough (4.0 ghz or higher), a Phenom II quad core will outperform a core i3.
Another upside of AMD Phenom II chips is that they are better than bulldozer (lol, sorry, couldn't resist
). No I'm not a fanboy.