1. DOs don't learn 'more' than MDs. They have, for the most part, identical pre-clinical years with additional OMM training for the DOs. However, this isn't really 'more' as far as learning medicine is concerned, more an additional tool you can use somewhere down the road (if you choose). It probably seems like you should, but trying to say DOs are 'more' than MDs ... will start a flurry (ps I know, I'm a pre-med ... anyone can reject what I say if they choose)
2. DOs focusing on primary care isn't a blanket statement. There are a lot of DO schools that put a lot of studnets in PC residencies and have a lot of PC themes woven into their philosophies, but your simply going to medical school to become a physician, and specialzing is very fesiable as a DO.
3. Gas - you can go ACGME or AOA. Most people say ACGME is the 'gold standard' but DOs are very well represented in ACGME gas. This leads me to believe if you make yourself a competitive candidate, you can match it.
Rads- competitive, you'll probably need to go AOA. I really don't know the stats for DOs in ACGME Rads, but I'm guessing it's fairly low.
PM&R - very well represented with DOs in ACGME, I think there are only a few AOA residencies. One of the few where you can really use OMM, and I really don't think there is any bias towards DOs in this field. The head of the PM&R department at Harvard is a DO.
Derm - suit up, because you're going to war. The thing about derm is that it's the most competitive all around right now. Look on the MD side of the fence, you have people with perfect step I, tons of published derm research, great derm LORs etc ... and don't match. These people then go do research or get a freaking PhD (exaggerating ... but only a little) JUST to match derm eventually. With that said ... matching ACGME derm as a DO is pretty much out of the question. There are 1-2 people who do it every year ... these people are rockstars, and (no offense) you probably won't be one of them. With that said ... you can match AOA derm, but the spots are small, some are unfunded, and you basically have to be just as good, but on the AOA side. The pacific derm residency through Western says their desired candidate are top 15% class, 85th percentile COMLEX, LORs from osteopathic derms, etc etc. And these are 'desired' qualities to possibly interview for a spot at an unfunded derm residency. People drink sheep's blood and sacrifice their first born for derm ... if you want it, do that.
Wheww ... rant over.