The i7 would win benchmarks, especially those that take advantage of it's hyperthreading. For standard game play at decent resolutions however, the difference will be next to nothing and you'd have saved a considerable amount of money. I'm not in favour of either in particular but contrary to popular belief, i7 isn't as far ahead as many think at this price point.
As games become more CPU intensive, the difference does become a little more apparent but the 533MHz clockspeed benefit of the Phenom II evens that out once more.
My next question is, will you be overclocking?