I personally don't know much about the internal workings of a CPU, I would be interested to read some articles if anyones got links. I have always been with Intel, had no reason to go anywhere else, so I can't really compare, other then to say that Intel have worked well for me.
I have read a bit about HT and 64bit, personally I think they are going to eventually merge the two technologies and disband 32bit, and the likelyhood is that it won't stop at 64bit. I don't know how long it will take, but I expect it's going to go up again sometime in the next few years, considering the 'expotential' advances being made by hardware manufacteuers.
Although, some predict that the focus of CPU specifications will not be on operating frequency but in bit capacity and in what technologies it supports (like HT).
Either-way, in terms of future proofing and planning, it's not going to be hardware that the general home consumer is squabling about, it's going to be software.
RC