As per Careers360 ratings both are having not much difference.
Both are good colleges for medical studies.
You can check the rating and reviews for both below:

MGMMC Indore ratings

RNT medical college rating

Hope this helps.
Good luck.

As per the rating and reviews, both the colleges are good and have got almost same points. So I would suggest you to consider your interest and convenience before choosing the college.

To check the college rating and reviews, you can go through the below links -

Mahatma Gandhi Memorial Medical College, Indore

RNT Medical College, Udaipur

Hope this helps!!!