[eluser]skunkbad[/eluser]
It sounds like your database would still remain somewhat the same, and if that's the case, I'd leave everything all in one application. Through routing and separate controllers, there's no reason why you couldn't just use a single authentication solution and have what appears to be 3 different websites all in one. Community Auth is set up to do this for i18n. Think about requests that come into the server for the three websites. If they all point to the same application, and if you code properly, you only need one app.
Also, not to toot my own horn or anything, but because Community Auth has so much done in terms of basic user management, there's really not a whole lot of work left to do to turn it into what you need. You'd probably spend more time re-styling the app than actual dev work.
