I didn't say what was best, I said that comparing "only" MHz is missing part of the picture. Today machines are easier to compare because they have similar functionality, but back in the day it was different.
I had a ZX Spectrum +2A back in the day and I've programmed several games for the speccy, and the attribute clash was a pain :)
It's well know that Speccy is more funnier that the C64 :D
Of course, it goes without saying that the spectrum was best.