Nicholas R.wrote a review of Patagonia Nano Puff Hooded Insulated Jacket - Men's on June 13, 2012
Awesome warmth to weight ratio. It packs down small. Stuff it in a backpack and you hardly notice it. I'm 5'9" 145lbs and use a M. The small turned out to be a bit too short on length, although, the arm length was okay. Both sizes would work, it just depends how you intend to use the jacket. S for layering, M for your outside layer. I love this jacket. My only problem, it that when it warms up to around the 50's, its too warm.