Actually, outside the US, the DO training is 7 years, same as a medical doctor. I chose a DO for my primary care doctor because they have papatory skills (i.e. they actually touch someone) that regular doctors refer out.

Actually, a DC goes to school for 4 years to learn what they do. A PT used to go for 4 years undergrad, then 2 years for the MS. Now you really can’t practice without a PhD. When a DC says they can do everything a PT can do plus Rx certain things, it really pisses PTs off. They work within the scope of a MD’s direction. DC don’t. Both use Phillip Greenman’s Principles of Manual Medicine in their training (an Osteopathic text).