I'm a DO students and my brother's a MD. So I've seen both sides so to speak. So the differences:
(1) As a DO you wont be able to go into some fields like Integrated Plastic Surgery. But then again, 95% of students in USMD schools wont be able to either due to grades and usmle scores. So as a DO, you have 100% chance of not getting in, while MD has 95% chance of not getting in. But if you're interested in things like Anesthesia, EM, there's plenty of DO's getting residency in those fields. For things like ortho, neurosurg, derm, there's DO funded residencies. So if you're a pre-med, in top 5%, and you're 100% sure you want to go into Plastics, you should probably go to MD school. But for things like IM, EM, neuro, peds, psych, a DO degree wont hold you back provided you have the grades.
(2) OMM + omm lab takes 3hr/wk so doesnt take away from our learning time in other classes. But I'll admit, we do get less histology, not that I care much for histo.