Both are damn good, just buy whatever you would be more comfortable with and don't waste tons of time deliberating on it as I have.
Here's a direct comparison of the two (direct link may not work):
http://www.tomshardware.com/charts/...compare,1403.html?prod[2884]=on&prod[2607]=on
Here's also a direct comparison of clock speed differences between the 955 and the i5 (with turbo off).
http://www.legionhardware.com/document.php?id=857&p=1
955:
- Better socket longevity in terms of future upgrading
- More developed platform
- Cheaper
- Very easy to OC with the unlocked multiplier
- Runs cooler & potentially quieter
- Runs current games at roughly the same FPS as the i5
i5:
- Faster speed clock for clock
- More powerful when overclocked
- Much more power-efficient
- Will outperform the 955 with most non-gaming applications by 5-15%