How do insulated jackets compare to fleece? I'm especially curious about their relative advantages and disadvantages across different ranges of activity, namely cross-country skiing, hiking, and just standing around.

Erik

Expert Answer:

Both types of insulation excel in their place, but are less efficient when used out of context. Efficiency means the amount of insulation for a given weight and bulk, along with breathability, ease of drying, and effectiveness when damp. Here's how the stack up:

Fleece

		Thinner grades of polyester fleece allow gradual changes in the insulation in your layering system to accommodate changing conditions.
		More than two thin layers of fleece starts to become inefficient, but I rarely need more than two layers of light or medium fleece when I'm active in the mountains, even in winter.
		When you are less active and need lots of insulation, thick fleece or more fleece is not as efficient as the more compressible, and lighter, insulated garments

		The highly compressible insulated garments are great to carry in your pack for stops and in camp.
		Insulated garments usually have slippery outer and inner fabrics which slide easily over other layers, creating a feeling of lightness and unrestricted movement. Too many fleece layers feel constricting.
		The lighter the fabric on the insulated garments, the better — it doesn't insulate and you already have one windproof shell.
		Insulated garments with synthetic fills are relatively unaffected by moisture, and consequently they can be used when active if necessary. However, they make big steps in your layering warmth — not the incremental ones you need while active — and don't breathe as well as fleece.
		Insulated garments with down fill provide the greatest warmth in relation to weight and bulk but are easily impaired by moisture and are best suited to drier climates and inactivity.

I've been using the The North Face Cerro Torre PolarGuard 3D jacket ($165) as the"extra-warm" sweater layer for rest stops and really foul weather for a couple of seasons, winter and summer. I like its compressibility, comfort, light weight, and furnace-like warmth.