My personal opinion: PE > SE > partial serrations
PE can do everything a SE can do, but not vice versa. Ex: Try cutting wood with SE. Also, I have easier time sharpening PE.
As for combo edges, I just plain do not like the aesthetics. Also, unless you have a very long blade, the serrated portion is not long enough to take full advantage of SE, and the plain edge portion is not long enough to easily cut things like wood. Also, when I am putting a lot of force into what I am cutting (ex: hard wood), I like using the part of the blade that is closest to the handle. Obviously that is a no go with a combo edge.
Again, just my personal opinion and experience.