I use XP Pro at work, 2000 Pro at home.
My home system gets pushed way harder
than the one at work (that is, the apps I
run are more demanding). I'd call the two
equivalently stable in that I can't really
recall the last crash on either one.
I haven't had any problems with hardware
recognition on 2K Pro, and that box has all
of my odd bits -- jog/shuttle control, video
capture card, graphics tablet, film scanner,
etcetera.
So, to twist rubicon's words around, I'd say:
"2000 Pro.
It's got all the guts of XP without the
useless window-dressing."
And it doesn't think it ought to phone up
Microsoft to discuss my computer