KGMU Lucknow has overall 2nd rank and BHU has overall 3rd rank. 

According, to Careers 360 both the colleges have AAAA+ ratings which means outstanding. Both the colleges have good placements, Faculties, exposure and Infrastructure. 

You can opt for KGMU as it has overall good ratings.

You can also check the ratings and reviews of both the colleges from given below link

BHU Ratings and Reviews

KGMU Ratings and Reviews

All the Best!!