I have seen links from this forum to my article (amd64vsi386.pdf).
The main point of benchmarks that I had done was to test wide range of software - not few specific programs but verify common tasks that computers are used for (multimedia,servers,games,math,3D) and see what are the advantages, in certain cases there are but sometimes no.
I think one of the problems with most of benchmarks that they use "standard benchmark tools" - like FPU speed or RAM speed that compare different HW (the speed of RAM/FPU will not change on same HW). What you need to compare is "same software" compiled for different platforms.
So IMHO tests like "RAM speed" just irrelevant in case of 64 vs 32 comparison.