Which is course option is better among PGDM and MBA for doing PhD and taking NET exam?

Both, PGDM and MBA syllabus is similar. You can choose any among MBA and PGDM to get admission in Ph.D, provided theses are done from a recognized universities or B-schools and degree awarded is approved and equivalent to MBA by Association of India Universities (AIU).

PGDM is equivalent to MBA, so if you do want to pursue Ph.D, you will be eligible. If you pursue PGDM from an AICTE approved college. There is not much difference between MBA and PGDM. MBA is offered by University recognized by UGC, whereas PGDM is offered by colleges approved by AICTE.