mini: it will look good on a certain height, if you are too tall it will make you look even bigger. I am 5 feet and mini is perfect. I am a minimalistic girl, in my bag there arent much. Lipstick, mirror, blotting paper, phone, wallet, sanitizer, handcream. I fit all those inside my mini WITHOUT stretching it to the fullest.
IMO, i think mini is more versatile, it can be brought out to many events, formal or informal. You can dress it up or down depends on the color of your choice. Mine is black.
m/l: i have tried on the m/l, def can fit more than what i need, more room. However, I really dislike the length of the strap.. i wish it could be worn crossbody without looking weird.
m/l was meant to be worn over shoulder, strap drop 9". while mini is meant to be wear crossbody, thus the length 20"
I attach my photo wearing mini black for you to see its size comparing to a petite girl