XP Pro is not hugely different to XP home - main differences are well summarised
here
There is little difference in performance of comparable tasks on comparable hardware.
Big difference to Vista, of course!
Also, there is no difference at all between OEM, retail or VLK distributions of XP (other than XP home is / was not available via VLK,
AFAIK), apart perhaps from SP levels. All the system files are the same.
So your good experience is likely to be down to running a very "clean" new installation, without much of the cr@p that system builders tend to clutter new PCs with (loads of unnecessary startup services and applications).
SD