The main issue is the length of the jacket , if you want the jacket to be till the waist take s, and if you want the jacket to be longer then take m. Other than the length there is no big difference
Bro I'm 5'8-9ish and I'm 70 kgs pretty muscular like broad. Shoulders and small waist i swear it on top of a black t shirt i have S size which gives kinda look of a little over-sized jacket which lookkks good. I swear it's the best one from h n m
