Among VMMC, UCMS and PGIMER (and the RML hospital) which is the best for an MD in general medicine?

Among the three option mentioned, PGIMER and RML hospital is the best option for doing an MD in General Medicine. It offers great exposure and academics. The spectrum of cases, facilities available, quality of care offered is exceptional. Other than Oncology, you will have exposure to all subspecialties.

UCMS is almost in the same range. However, it has a locational disadvantage. Other than that the spectrum of cases and academics offered at the institute is quite good. 

VMMC is also a decent option. But it has a high patient load. Academics are really poor and you will have to go out of your way to learn things.