I don't think it really matters as the classes in MW & OB were just basic presets for those just wanting to jump in without having to design their own. One thing we can see in these classes was Spellswords never got conjuration whereas Battlemages did (giving battlemages the opportunity for either bound weapons or summoning allies).

I'd go with robes, if only to differentiate my mage characters from my warriors and archers.

I do like spellswords though, but I generally have them wearing robes with armor on hands, feet and head (or a dragon priest mask).