Both are excellent colleges undoubtedly and tough choice to make. 

AIIMS on one hand is excellent brand but considering Nagpur Brnach,, teaching is average as compared to Delhi and so is training and hands on experience given. 

GMC on other hand is too good for live cases and breadth and depth pf cases been observed which give studnets really good hands on exposure adding with topnotch placements . 

Henece GMC looks much preferable.