Here's a 6'2" guy modelling a medium Marmot Zeus down sweater on the Zappos site:
http://www.zappos.com/marmot-zeus-jacket-dark-azure
The Zeus and the Quasar have the same 28 inch back center length, so you can get an idea of the length. The Quasar is cut slimmer through the body and waist than the Zeus. My Zeus is sized to wear over mid-layers for me and, in fact, I can wear it over my Quasar Hoody — not big, big like a down parka, but ample through the body. The Quasar is athletic. I can wear it over a power stretch fleece, but that's about it. So it's going to be trimmer than the medium Zeus looks on this model.
I don't think length will be a problem for you with the medium and probably not even with the mens small (1 inch shorter sleeves and body length is probably a good guess). The question will be the cut through the body. The Quasar is definitely a slim/athletic cut jacket, so worst case is it would be a little big, but not a tent like a men's down parka.



