I am a B.Com-B.Ed. What would be more beneficial: doing a PGD in Education Management or MA?

You should go for MA, and after that, you can go for Ph.D and lectureship. If you do your Masters and further studies, then you have a bright career ahead. All the best.

Since you are already graduate, you should now see what career you want to build. Then do the course accordingly. For teacher you have to appear in the TPT/NPT exam. So, maybe an MA would be better as it may give advantage in schools. Also degrees are always better than Diplomas.