That's a loaded question, but I'll do my best. My family has made a living from DO school administration from decades, and this is what my parent tells me.
First of all, none of the schools are "easy" to get into. Only 1/5 applicants get accepted to DO school (as opposed to 1/2-1/3 for MD).
That said, it's generally felt in "the business" (hah!) that PCOM, CCOM, TCOM, and UMDNJSOM are the tougher schools to get into. These are the schools that generally get applications from all over the country (Texas gets primarily in-state applicants, but Texas is larger than France, so it's pretty much the same) AND from large, concentrated metropolises, resulting in highly diverse, highly qualified applicant pools. PCOM and UMDNJSOM are also less focused on OMM and primary care, making them more like conventional allopathic medical schools than paradigmatic osteopathic once. Huge percentages of their grads specialize, and they draw a lot of would-be MDs. I'm not aware if this is the case at TCOM and CCOM. Also, I'm told that PCOM receives the most amount of applications of all the DO schools, while UMDNJSOM has only 75 slots to fill and very reasonable tuition, making both schools highly competitive.
Something else to consider in DO admissions is that, when applying to an out-of-state state school, your chances of admission are slim unless you're really stellar. I'm thinking here of Michigan State, Oklahoma State, UMDNJ, TCOM, OUCOM, and Pikeville (though it's not a state school, you have to either be from the area or do a great job proving that you want to practice family medicine there).
I wouldn't put too much stock in which schools are more competitive, though. It really makes no difference. What I WOULD consider is that, out of all the DO schools, the ones with the best academic reputations are PCOM, NYCOM, and TCOM (this is NOT my opinion, please don't yell at me). NYCOM, as the largest medical school in the United States (320 places per class), is not the most competitive school to get into, and stories of people being accepted with 21 MCATs are not uncommon, but their education is definitely in the top 3--very OMM-heavy, but not so much primary care. (I go away to school at NYIT, the school where NYCOM is located, and this is what students tell me. I don't recall ever meeting somebody who didn't think NYCOM's education is top-notch.)
Hope that helps.