Here's the dealio:
1. No school is going to really give you a better chance of specializing. It's up to you. Get good pre-clinical/clinical grades, good LORs, rock whatever steps you take
2. Forget ACGME derm and plastics ... 90% of MDs can't match ACGME derm or integrated plastics. Like Team said ... a few DOs nab some really amazing ACGME stuff that only the robot, ACGME gunners get every year (the ACGME derm from CCOM a year or so back, the Rad Onc from Western in 08, etc), however, for the most part ... just forget it from the MD side. Go check out the derm forums and read some HEART BREAKING stories about people with 260+ step I, AOA, perfect grades, derm LORs, etc, who just flat out don't match. It seriously sucks.
... the silver lining ... AOA residencies. The AOA funds (kinda, lol) its own set of residencies in derm and PRS and they are only available to DOs! This greatly increases you chances, etc:
http://opportunities.osteopathic.org
3. Remember that you will change your mind in med school or may not even have the numbers for these fields by the time rolls around OR may have them but not want them anymore. Times change, things change, so go in with an open mind, work hard to keep your options open, and match. Good luck.
👍
Oh and with regards to the original question ... I'm willing to bet that with AOA residencies, it's really equal for DO to specialize compared to MD. People can debate this err whatever, but I've heard the same from a few DO students who went through the match.