[FanIn80]

I can't believe no one mentioned the cores yet. While I'm not completely sure of the ramifications, the i7 registers as having 8 cores in Windows while the i5 is only 4. I know 4 of those 8 cores are supposed to be virtual, but I'm sure someone else here can explain it better than I can.

Also, the i7 will use dormant cores to overclock itself on the fly. There's no way it gets outperformed by an i5, unless it's in a very specific setting. I'm willing to bet whoever told you that was probably just looking at the i5's higher GHz rating and extrapolating from there.

Edit: As an example of the overclocking feature, my 1.6GHz i7 will use unused cores to overclock itself to 2.8GHz on the fly. That's the low-end i7, too.