read some reviews of the core2duo's... the heat issue is gone... the C2D's are NOT expensive for the speed The $316 Intel E6600 is Faster than AMD's $600+ FX 62
Yes, but those numbers are in the context of multi-threaded benchmark apps and games, mostly. In the average-consumer world of single-threaded apps--Internet browsing and email--Intel's performance advantage vanishes, AFAICT. A $100 single-core Athlon 64 3500+ beats a $100 Pentium D 820 all day long in single-threaded applications, and keeps up pretty well with the multi-threaded.
You're right about the heat issue, for now. Intel's 65nm process has bought it a big lead there for a while. As for the actual architecture efficiency, I'd still guess they're much closer.
As always, the final answer depends on how the machine will be used. And other components will nearly always make a bigger difference than the CPU.