Ok, I just received this jacket about an hour ago. Go with the small. You will have room in it for a jumper unless you are a fatty. I am taller than you (6"2) but skinny and the medium I ordered is pretty much spot on for me. (I usually wear a large). I will attach a quick sexy webcam pic for you - note: I am 6"2, have a t-shirt and long sleeve top on and the jacket over that. I have full movement and prefer the jacket in a "not too baggy" style. Btw, it is a nice jacket - similar to what I would expect a snow ninja to wear - lining has apparently been designed by retarded children but apart from that it seems warm. I too wear the 686 Smarty cargo pants in medium. They are good pants. Jacket seems to have been constructed with slightly different materials and not as insulated as the Smarty cargos which was a bit disappointing, and no snow ninja would accept the fact that the pocket flaps are velcro phonies but regardless, I like and would recommend the jacket.