It really depends . Do you have 38" chest or a 44" chest? Do you want to wear over fleece,and LS baselayer, or not?
Im 5-10, 155lb, 6% bodyfat, 31" waist, 42" chest , and I wear a L EX-light, fits snugly over 100wt fleece. About perfect for me.
My L nanopuff which was bought when I weighed about 195, is HUGE now. I need to get a thermawrap.