Hi aspirant first of all let me clear you this thing that KGMU, Lucknow is a state owned Institution whereas AIIMS, Raebareli is a deemed Institution. So for better comparison in between both of them I would like to suggest you the college predictor tool careers360(link mentioned below) where you can not only compare two colleges or institutions but four colleges or institutions at a time.

https://www.careers360.com/compare-colleges?icn=college-compare-landing&ici=question_detail

Good Luck.