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Sync how? Through .mac? I think .mac is through the internet- you wouldn't even need to wait until you go home! But... I think it only syncs stuff like safari bookmarks, address book, and ical. Nothing data heavy like an itunes library from what I understand.

I actually have the macbook/imac combo and like it a lot, though I have no syncing solution. I'm curious if there is a free way to sync your ical and address book, even if it requires proximity as you seem to describe.
 
Two computers is more flexible than one, and you have a backup machine in case one goes down, but if I were you I would get the MBP.

Performance AND portability on one box without having to worry about syncing anything. Just make good backups.
 
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