A solo enchanter can get to 65 faster than any other class if they know where to go and when. They are the gods of self powerleveling.
But when you're 65 there isnt much difference between the duo's 99% of the time. The mobs you can kill are pretty universal as will be the ones you simply cannot kill because they nuke or hit too hard, or too frequently, or because there is simply no way to pull one single.
Of course I like the Mage-Wiz/Cleric duo myself. It's probably the best group aiding duo you can have especially when there is a shaman in th aprty you can trade heals off with with your cleric while swithcing over to mage to nuke while your heals are channeling.