Other than the convenience of online learning, know yourself. Are you very self motivated? Can you organize your academic life? Do you find that you don't need to talk with people, interact with fellow students face to face? One suggestion is to take one course as a trial run.
See if you respond well to the asynchronous aspect of the course and the lack of social aspects in your learning experience. You can also then test the online institution as well. How available is the teacher? How well run is the course? Does it take a long time to get your test grades back? Is it too easy or too difficult?