Well.

Do schools are good, but it is not harder to go to a DO school just because of the osteopathic medicine component. Many MD schools have unique aspects to their curriculum that make them "harder" than another school.

I have nothing against DO schools as I considered attending a few my self, but if the majority of BYU students going to med school go to DO schools it is because most of them didn't get into an MD school (not all, but a majority)