The Patagonia M10 jacket is our favorite hardshell for backpacking and the lightest jacket that we tested. At $399 it is also one of the more affordable hardshell jackets in our review, although by no means the cheapest. Our tests show that this jacket is more durable and more versatile than other light shells and nearly as tough as jackets that weigh twice as much. Advanced fabrics and streamlined features make the M10 fantastically versatile; it's small and light enough to accompany you anywhere and it is one of the most comfortable jackets we tested.
Though the Patagonia M10 is fantastic, our testers prefer the Arc'teryx Alpha FL (4 oz. heavier) for alpine and ice climbing and backcountry skiing because of its more ergonomic fit, larger chest pocket, better aesthetics, and astonishing durability. For many people, and backpackers specifically, the M10 could be the best hardshell due to its extraordinary light weight and tiny packed size. It does come with a laundry list of limitations, however, and thus is only recommended for someone who needs a very specific type of jacket.