There is not so much difference in both the degrees. Its just depends on the college how do they are capable to provide placements to the students.

The main reason why postgraduate courses are named as PGDM is because when an Institute is an autonomous body (not affiliated to any University) and conducts management courses, then such Institutes cannot offer MBA degree.
So the course will not matter but the level of college you do it from will have an impact on your starting pay package.

Both the courses are equivalent if done from prestigious colleges as well as iims.
Only the name of the degree differs.
Also every iim offers pgdm which doesnt affect their reputation.

Almost equal. Yaar ..but specialization in matter of fact