There will always be exceptions to every situation.
I remember reading about the psychology of playing good vs evil (implied) years ago. Unfortunately I can't find the article to cite it. Basically the theory being presented was that younger players tend to gravitate toward move good, or "heroic," factions, based on a number of reasons. Younger kids tend to root for the good guy. They're still being taught (hopefully) that you should be a good person and help others in society. They just haven't reached the point where they find out that it feels good to be bad (opinion I know).
This article was no scientific study, or any official psychological profiling, but it was interesting nonetheless.
I disagree with your thought that "professionalism" is tied to "time spent playing." I would argue that professionalism is based on how an individual or group carries themselves, how they work with others, and how open they are to receive criticism and/or suggestions. IMO, the said "evil" factions have always been more professional. But that is solely my experience.