Basically, unless you're certain you want to be a Dermatologist or some other exceedingly competitive specialist, there is little difference between the two.
MD and DO schools generally have identical prerequisite coursework. MD schools generally place more emphasis on scientific research experience prior to admissions and are more selective about grades and MCAT scores. DO's are less emphatic about research, and somewhat less hung up over academic credentials (though still very high standards are in place), and appear to be more willing to consider other factors when choosing who to accept.
Both MD and DO schools value service, clinical experience, shadowing, and demonstration of interests outside school (well roundedness).
I've met people who were rejected from MD schools and accepted to DO schools. I've met people who were rejected by DO schools and accepted at MD schools. I've met people who were accepted to both types of program. And I've met people who elected to only apply to one or the other.