i wud vote for both XP and Vista, for everyday use and MAC for the more "profestional" use.
Vist - XP are pretty much the same, u dont need a fast ass comupter to run Vista like ppl say, just disable the start up programs to the basic 17 windows needs and its fine PFU i use it roughtly 350-400 (on XP uses 150-200) and the ram it uses is reduced by 70% from the 756 to load up on start up to 328 (somethin like that ^_^).
Vista supports HD better so tbh Vista would win due to the HD performace beeing more updated.
so TBH Vista for Everyday Use
MAC's for profetionl use.
theres no comparison really