A subtle difference is that the MM.Classic has a step in its profile. That makes it both more user friendly and competition friendly. It will tilt less, and slowdown less; basically, it is more forgiving to sloppy technique. Either way, few people would carry O shaped yoyo's into a competition.
The size and shapes are fairly similar, the MM.C is slightly larger in both directions.
Overall, the MMC would be better, but I would say that, for half the money, the Bench O is a far better deal(cost vs performance).