On bare metal it's a different story, though, but I still would think that there are more virtual servers than real ones.
And what difference does virtual versus physical machines make? Heck, you can even run virtual 64-bit guests on a 32-bit host machine if the CPU supports either Intel-VT or AMD-V.
But interpreting those results indicates to me that there are possible problems with this platform where f.ex. file copy performance is ~50% faster on 32bit than 64bit.
To me just assuming that there is no difference and go with instinct without anything concrete evidence is the wrong way to go.
As the OP seems to have suggested, virtual machines don't have a lot of memory.