Quote from Toms Hardware reviewing the i7 vs Phenom II processors
"If you’re instead buying for a more productivity-oriented purpose, the Phenom II makes sense. After all, it’s able to handle every task nearly as well as i7 does (both platforms overclocked, of course), it drops into existing AM2+ motherboards, it costs less, and in a majority of situations, will use substantially less power—even highly-tuned, as we’ve done here. We didn’t have as much luck overclocking the Phenom II as we expected, but the chip is still a notable improvement over AMD’s 65 nm Phenom series."
Toms Hardware review