If you plan on hardcore overclocking, go Intel.
If you plan on moderate ocerclocking, a matter of preference, though most Q6600s can reach 3GHz without a voltage bump whereas Phenoms only can go up to around 2.6-2.8GHz at stock volts. I've heard Phenoms getting up to 3.4GHz, but they run way hot at those speeds. Thenagain, as I said if you're into hardcore ocing go Intel.
If you plan on running those things at stock speeds, I would get the AMD simply because it's $5 cheaper, and those two CPUs perform about the same. At stock speeds, spending the extra $5 gains you absolutely nothing. Thenagain, it also depends on can you find a good, reasonably priced mobo...
EDIT: Also, Phenoms abolutely destroy Intel CPUs when it comes to floating point calculations (this makes Phenoms good for 3D rendering and scientific applications & such, but for an average user, well, it really means nothing unless you play 3D games with a software renderer

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