This is a classic example of false advertisement. A master's degree is a master's degree. It cannot be equated with PG Diploma courses just because these B-Schools or premier institutes do not have the authority to issue any degrees because they are not formal universities affiliated with the University Grants Commission. Such institutes are mushrooming every day in every corner of India, have no quality but just a money-making fancy college formula to spend money lavishly on education. After all, what matters is the quality of the brain that cultivates and yields the best Nobel scholars. These institutes have no credibility because they don't produce Nobel Prize nominees or winning students in their institutes.
First of all, both PGDHRM and PGDBA (with specialization in HR) are both Post Graduate Diplomas, not technically a Master's Degree. Secondly, there is no point in wasting your time and energy going for PGDBA (with specialization in HR). Just go for PGDHRM as that is totally focused on HR. If you opt for PGDBA, you would also have to study subjects on Marketing, Finance, etc., which are not really related to HR. I myself did PGDHRM and want to tell those people who call such courses/institutes 'informal' that I got my break in HR to a large extent because of PGDHRM from Symbiosis. At the end, don't depend on anyone: make your own decision. Since you seem serious about pursuing a career in HR, go for some distance learning course from a reasonably good and recognized institute. I am now pursuing a Master of Labour Management from Annamalai University; it is a 2-year Degree course. If you are bent on acquiring a degree, then you could go for an MBA from Annamalai with specialization in HR, and yes, it would be a Master's Degree in HR. Above all, be cool. Cheers!