The intel Core 2 Quads are true quad cores, just not as efficient. Well... that's my view on it.
As for clock speeds, they've been shown to help, however the netburst architecture was very efficient when processes per cycle. And you can overclock AMD CPUs as well to get higher clock speeds.... just you have to compare it to a intel C2D when at stock (sometimes).
AMD was the first to be efficient in processing per cycle. Intel eventually caught on that higher clock speeds didn't work. However, I still think AMD wins in the low to mid-range market because their CPUs still perform very well, especially when given a 400-800MHz boost.