I would use professional.
I think premium is a waste of money.
Makes zero sense to me, please elaborate. Does the extra cost for Professional benefit his tasks in any way?(Things like XP Mode would be good if he's into older games, but otherwise, i don't see the justification).
BTW OP here's a compre and contrast chart of the different features in the Windows 7 line: http://windows.microsoft.com/en-US/windows7/products/compare?T1=tab15