Well, I'll give my two cents about your questions, and I'm sure everyone on this website will be happy to give them your opinions as well.
When it comes to the ability to practice medicine, yes, it doesn't matter.
However, it's the type of medicince that you want to practice that could be a difference. Though both MD and DO can do general practice or specialize, most osteopathic physicians tend to enter family practice rather than specialize. That is because there is a stronger push for DO's to enter family practice. Also, if you are interested in learning osteoapathic manipulation, then you can apply this manual medicine as a supplement to the conventional medicine you will practice, or even if you desire, solely practice osteopathic manipulation. The OMM is another tool that an osteopathic physician can use to diagnose and treat a patient than an allotpathic physician cannot.
As to applying, there are different types of pre-meds. You have the pre-meds who have decided that DO is the way for them onlyl (like myself), you have pre-meds who take the "shotgun" approach and apply to both and will take any school that will take them, pre-meds that apply to both and use DO schools as backups, or pre-meds that have been rejected from MD schools and apply to DO schools just to become a doctor (MD wanna-be's).
If you apply to DO school, you should really want to become a DO. I feel that though there are many similarities between MDs and DOs, it's the difference that counts. You have to realize that if you become a DO, you may have to explain what a DO is to the layperson, and you may face some prejudice because of your choice. But, if you really are happy being a DO (which I will be) then none of that will matter.
My advice: research all that you can about osteopathic medicine. This website is a great place to start. Volunteer/Shadow a DO and ask about their experience in medical school and in the medical field, and if you can, try and find one that does OMM (this does make a difference!). Go to an osteopathic awareness conference at a med school, or just visit an osteopathic medical school and see what they are all about. After doing all that, you should know if you really are genuinely intersted in becoming a DO.
I personally think that applying to both shows that there is some doubt in a pre-meds choice. The truth is that it is easier to get into DO schools, but that is because DO schools tend to look more at the entire applicant than just his/her numbers. I mean, if you don't believe in the philosophy or in the applications of osteopathic manipulation, then why apply to DO schools. If that's the case, this type of person should only apply to MD schools and leave the spaces open to students who truly want to become osteopathic students.
Just my two cents.
Arnold
Western U/COMP Class of 2004