It don't matter.
Nio matter how you cut it, the fastest box will be running the best OS with the best backwards compatibility.
One of the reasons I am a Mac user is because I don't get hung up on bits and bytes. I get hang up on how fast and how WELL I get done what I need to get done.
On those fronts a Panther running G4 laptop or G5 desktop will rule the hill.
The rest is just trivia. By the time that 64 bit OS form MSFT can run ANYTHING you are running today, you'd be in a nursing home, probably.
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