You have an 18 mo old Vista installation that's snappy? My wife's lappy came with Vista non-snappy out of the box standard. It also came with all of my XP administration features renamed for no reason at no additional charge.
That being said my XP installation get's re-ghosted every 9mo or so; I suspect many slashdotters have had a similar experience.
Generally speaking, I agree your preference is the reason you would choose a Mac (whatever that bias is formed by, perceived system performance included), however your invariable Windows stability may be a unique phenomenon.