Except that if you buy a Mac, you *can* run XP natively full speed, with drivers, and bypass the Vista disaster entirely!
That's precisely why I've got Macs for notebooks and desktops these days.
But if the question is how to run XP on Vista-only hardware, a Mac is not the answer.
Full disclosure: even on a Mac, unless you dual-boot or install XP on the bare metal of the Mac, you can't really get to 100% native speed. Fusion is really good and quick, but there's still a couple percent of overhead. Wired ethernet network speed is one area they have some improvement yet to go.