Many people consider IMS BHU better than KGMU due to internal PG. But the truth is internal PG at IMS BHU will only give only a single attempt to get an internal seat at a low rank. Moreover, owing to the rotation system in a particular year, there might be no internal seat for a particular branch for a specific category. If you happen to belong to that particular branch, you will have to be among toppers else you won't be eligible for internal benefit or state quota. KGMU on the other hand, will give you unlimited attempts with a state quota
Also, I feel MBBS is not just about PG, but also about the holistic development of the students. That being said, the IMS tag isn't as valuable as the KGMU tag.
So, I don't think it's wise to choose IMS BHU over KGMU.