I see his point as well, however, DO schools gear their education towards the COMLEX.
You can be reasonably confident that the DO school you attened (any DO school) will prepare you well for this exam.
As far as the USMLE, if you choose to take this you will be doing a great deal of self-preparation.
Therefore, it seems that the school you attend does not make much of a difference in this case.
Sure, there are variations within the curricula of the different osteopathic schools, but as someone noted...with all of the variables that can factor into this equation, having the data means little.
Any DO school you attend will give you a good education. If you want to take the USMLE on top of that, then get the review books and study. Good grades in your classes in school will not guarantee a good grade on the test.
I also agree that there should be more similarities between the two exams. Maybe that way in the future residency directors will be more familiar with what osteopathic candidates bring to the table.