I want to develop an online application and I am considering EITHER building a website with community features built in or building ONLY a facebook app. I was wondering if other people have had to make the same decision and what things I will need to consider.
The website I want to build will be an educational portal where people can make and take tests online
I disagree with some of the other answers here. There is a huge difference between a) trying to advertise a new place on the web and b) trying to advertise a new functionality of an existing place. Even if this new website would offer a very tight integration with Facebook and some other social platforms. Keep in mind: facebook users really don’t like to leave facebook, no matter what the reason would be. That’s why the click-through rate for the advertisements is so embarrassingly poor: http://en.wikipedia.org/wiki/Facebook#Company
That said you can of course always do both: build a website and offer the same functionality through a facebook app. However my opinion here is that if you’re application only offers its users a single functionality, you’ll be better off just doing the latter.