As good as today聮s pile and fleece jackets can be, they still don聮t pack the warmth-to-weight ratio of insulated shells&$151;that is, pieces that have down or synthetic insulation wrapped inside a very light, (usually) nylon shell. They聮re simply loftier than fleece, and loft equates with better heat retention. The extra shell also cuts down on wind and evaporative cooling (the heat lost when moisture on the skin evaporates). And, their shell makes them great layering pieces聴an outer shell such as a Gore-Tex jacket can slip right over them.
The Cocoon PulloverBut, what to go with聴down or synthetic? Western Mountaineering聮s new Flight Jacket ($199; www.westernmountaineering.com) uses high-quality 850-fill down to create a very warm piece that聮s still very light, only 10 ounces! And it聮s a lot of jacket聴the Flight actually could be seen as a very light down parka. Bozeman Mountain Works聮 Cocoon Pullover ($179; www.bozemanmountainworks.com), on the other hand, uses Polarguard Delta, the newest iteration of that long-popular synthetic fill. It聮s even lighter than the Flight (8.5 ounces) but achieves that in part by eschewing features such as a full zip.
Other solid candidates include Moonstone聮s very fine Lucid Down Jacket ($160; www.moonstone.com) or Patagonia聮s synthetic-fill Micro Puff Pullover ($148; www.patagonia.com), which are each similar to the Flight and the Cocoon in features and warmth. I use a Micro Puff as a skiing base layer and love it.
Still, for backpacking, I聮d go with a down piece, either the Flight or the Lucid. I just prefer down聴it聮s warmer for each ounce of fill than synthetic. It聮s also softer, packs down more easily, and lasts longer. The two downsides are cost and water-resistance. But cost isn聮t really a factor here as both down pieces are competitive with synthetic. So what about the water angle? It聮s true that down can wet out, at which point it takes forever to dry and doesn聮t offer much insulation during that time. But when it rains you were a waterproof shell, right? And even if down does get damp, it takes quite a bit of water to really remove its insulation value.
So go get the Flight聴or the Lucid聴and stay warmer.