Too bad there isn't a middle-ground. I use both; the larger, more important, or more difficult the encounter, the more likely I am to break out the miniatures.
From a certain perspective, I prefer TotM because it's most adaptable, requires less prep time (I don't have to draw anything out, in advance or ad hoc), and doesn't run into problems with (for example) the Wizard player counting off squares to see how big his fireball is so that he can drop the boundary right between the Fighter PC and the troll she's in melee with.
On the other hand, minis are a lot less prone to misunderstandings, ambiguity, and similar complications.
Edit: I guess my actual preference is TotM. I checked minis because that's what we do most often. I've been intentionally working towards more TotM, though.