* Academics is the more common and generally preferred term. It's a broader term encompassing all those involved in higher education, including professors, lecturers, researchers, and students.
* Academicians is less frequently used and often implies a higher level of achievement or membership in a specific learned society or academy. Think of it as a more formal and potentially more exclusive term.
In most situations, academics is the appropriate and more natural choice. Use "academicians" only if you specifically want to emphasize membership in a prestigious academy or a very high level of scholarly accomplishment.