With all that has been said, just wanted to clarify a few points:
Ortho is competitive all around, and is going to come down to the individual student far more than the degree. If you're a lackluster MD student with an average USMLE score, don't expect any favors simply because you're an MD student. Those Ortho spots are going to go to the thousands of other qualified applicants. However, if you're a hardworking, dedicated DO student, don't expect to be doomed to a PC residency in Ohio. Go look at some DO match list, they put people into AOA ortho programs every year. For example ...
In 2008:
KCOM put 5 people into Ortho (and one in ACGME)
DMU put 7 people into Ortho
KCUMB put 7 people into Ortho
etc. Also, here is a link to get to the AOA (DO) Ortho residencies:
http://opportunities.osteopathic.org
The point I'm trying to make is a. You'll probably change your mind in med school b. Ortho is competitive, and not all people have the scores c. If you don't have the scores, a degree isn't going to save you one way or another. Like Law2Doc was saying, there are more opportunities coming from the MD side, but frankly, if you don't have the stats ... it's probably a moot point because there are more than enough highly competitive applicants for all the Ortho spots.
Further more, about the 'choosing a DO school' thing. There are lots of reasons why people choose DO schools. I know several people who've picked it over MD with no qualms, and it has nothing to do with a philosophy or lower scores ... it has to do with cost, location, family, and fit. My advice ... go to college, do the best you can, apply to places that are cheap, in areas where you would want to live, and near your family. When you interview there, make sure it's a 'fit.' I'd put this preference above MD vs DO. If you really want the MD behind your name, or you really buy into the conception that you can go to an MD school, slack off, and still match integrated plastics at Mass General simply because you go to a state MD school and not a DO school ... then good luck.
You've got a ways to go ... focus on more relevant things first.