Chances of find a private practice job after residency is usually higher in the area that you did your residency. This is because you get jobs by word of mouth. Your attendings from that program have connections with the private practice peers ... they might even have done residency together so they'll be the first to know if a job is opening up before that job is even listed online. That being said, it's not impossible to get jobs outside your immediate area but when dealing with someone who doesn't know you personally or have someone that can vouch for you the only thing they look at are your credentials. That's why it's easier to find a job AFTER several years of practice instead of straight out of residency.
DOs usually have their own residencies. That being said, there is very few crossovers of DO into MD residencies at least in California. Think about it. Everyone wants to come to california, so why would a program fill it with DOs or Carib/FMG grads if they have the pick of the litter from MD schools? Now I'm not saying that somehow DOs are less qualified than MDs, it's just that it looks bad when you have DOs in your program. People will think "why cant they fill their positions with MDs?" Anyway, it's not impossible. I've seen many DOs in different fields of MD residencies. However, I've heard of an upcoming change in terms of the AAMC saying they will no longer accept DO applicants in the future. I don't think this has been implemented yet but it's been in the rumor mill so there may be a possibility that if you do go DO you may not be able to match into an MD residency in the future. But again, DOs have their own residencies and they match into fellowships too so it's not impossible though I'd probably play it safe and just take the MD.