According to the reviews online by the students of these colleges, here’s what the ranking seems to be like:

• KGMU has mostly been ranked among the top 5 institutions in India. It usually maintained its place in rank 2 or 3. This institution is 125 years old with proper educational experience.
• AFMC is a very disciplined institution with strict rules and codes of conduct, as it has direct affiliation with Armed forces. Though being well reputed, in academics and exposure it might lag behind.
• MAMC, Grants Medical College (GMC) and IMS BHU are at a similar level.
• Some students claim MAMC to be slightly better than AFMC. 
• GMC is very popular in and around Maharashtra.
• IMS-BHU is autonomous; it has the reputation of BHU tagged along which is beneficial.
• CMC is amongst the oldest medical colleges, but their severe lack of proper facilities in this college and political disturbances have tarnished its reputation.

Therefore it is suggested you either go for KGMU or MAMC, as they will provide you with the required exposure and opportunities.