Vakid CAT/CMAT/MHCET/GMAT score with minimum 50% marks is mandatory for PGDM/MMS.
PGDM is best if you want latest industry experience and International kibd of learning experience blended with rich practical experience into Management.

PGDM is better because the curricum is flexible and upto the needs of today.
Many students are of the view that it is a Diploma course and not a Degree; you are right to an extent that it is a Diploma. The main reason why postgraduate courses are named as PGDM is because when an Institute is an autonomous body (meaning it is not affiliated to any University) and conducts management courses then such Institutes cannot offer MBA degree. Even IIMs, XLRI's doesn't offer MBA degrees they only give PGP Diploma or PGDM since they are autonomous and independent bodies. On similar lines AICTE  is allowing approved colleges to run a PGDM course. Some Business Schools offering this AICTE PGDM course need not be autonomous, the PGDM course will be autonomous given by the Institute & directly approved by AICTE.

Not necessarily that a PGDM is equal to MBA because if PGDM is to be an equivalent to MBA then the college offering the PGDM course must have accreditation from AIU.

Good Luck.