(Some) community colleges are competing on academic strength and quality of teaching. Transfer rate, and graduation rate (and/or graduation time) from the subsequent institutions are easily measured proxy metrics for academic quality (up to you to decide if they're compelling proxy metrics).

Class size is also a proxy metric for quality of teaching. If all your classes are auditorium lectures vs 20 student groups, it makes a difference. Of course, small classes with terrible instructors and awful lesson plans aren't better than competent lectures.

Of course, community colleges fill a lot of roles, and aren't just for transfer students, and they need to compete on those other things too.