The ONLY big advantage I see to medical is that the license applies to the entire practice, meaning if you have it on 5 computers you still only need one license. The other versions are only licensed for 1 computer.
This is the info I received from the vendor at the AC conference.
I have been using 8 preferred and it worked well, until the computer died. I didn't use it that much, since I can type and template faster except for complex patients, I have not reinstalled it on another computer yet.