Has there been any research done that contrasts point-based and achievement-based gamification methods?
Reputation is a recognition system for participation, while the badges represent the type of participation.

Reputation amasses over time simply by recognizing that the individual is participating in a meaningful way, and that their experience can be judged by the amount of reputation. Badges, on the other hand, show where their aptitude and participation lies (Such as being a prolific editor, having insightful answers, etc.)

Both of these will appeal to people in different ways, and both will contribute to a thriving site, as it encourages several levels of participation. The reputation will be more of a benefit system, as you get increasingly advanced privileges on the site for higher reputation, and the badges are the "pat on the head" motivation.

While I don't have access to the full text, the precis for this article suggests that they presented specifically on the Stack Exchange model, and the badge/reputation system as applied to an online community. Other than that, most of the gamification models that I found searching scholarly articles were more geared toward education and social media rather than Q&amp;A type sites.