Oral & Maxillofacial surgery is regarded as the most respected speciality in dentistry. This is because they do a variety of complex procedures, which include--but not limited to--impacted wisdom teeth extractions, bone grafts, facial reconstruction, and trauma surgery. They have to spend the most time after dental school in regards to specailization. Also, according to many legit sources, Oral & Maxillofacial surgeons are in the top 5 in highest paying salaries in the U.S.
You don't have to get an MD to become an Oral & Maxillofacial surgeon. There are two routes. You can do a 4-year program after dental school (no MD) or you can do a 6-year program (gets you an MD). From what I have read, there is no difference between a DMD/MD oral surgeon and a non-MD oral surgeon. Both are fully capable of doing their respective procedures. The MD is a nice addition which possibly gives more respect in regards to their colleagues and patients.