I really like when threads get revived that are older than I am on the forums. It makes me feel young. Plus, it always impresses me how people find these threads with like, one or two posts... or no posts! I'm like, "That's epic!"
Meanwhile, to the thread's actual question... I'm leaning towards Restoration because that's all I've played with right now. Alteration sounds really nice with paralysis. I think if Restoration had some more poison spells, which would make sense, then that would easily be my favorite. It's really fun running through a dungeon and completely wrecking draugr.
I keep playing with magic like I am with my characters then I'm bound to try a pure mage again. This time, though, I would rely heavily on Restoration and Alteration. Defensive minded first, offensive later.