The HF is definitely better than the MC in terms of SQ. The HF uses a true balanced armature driver, whereas the MC uses a new design "moving coil" driver that is a hybrid armature/dynamic driver. The MC does have a bit more bass presence, but it just doesn't have the speed and cohesiveness of the HF -- it gets pretty over-whelmed on busy music passages (e.g., By itself the MC sounds good, but when you compare it to the HF, the HF is clearly better. If you can find a gently used HF, you will be much happier, if SQ is you main goal.
About tips, the Shure Olives are extremely tight on the HF -- I didn't try them on the MC when I had it. But I didn't like the foam tips, and to this day prefer the standard creamy-gray colored triple flange tips on the HF and my ER-4P.