The Middle Layer For most people, the options for that insulating middle layer really boil down to just two. I'm not including down in the discussion, because although I own some down clothing, even in sub-zero weather I have not found a need to use a down jacket. Some people love down, it's wonderfully compressible, and even I have a certain fondness for my driloft covered down sleeping bag. But when it comes to middle layers, it's simply a matter of style. I can't answer that.
Fleece is certainly lighter, but a nice wool sweater has been many a hiker's best friend.
When his factory burned down, he kept his nonworking employees on the payroll until he could get his factory back up and running. That salesperson is going to march you right over to a rack of jackets and pants made with Gore-tex. Gore-tex is expensive, but for many people, it's worth the price. Many clothing manufacturers have a proprietary substitute for Gore-tex, but there is usually a difference. Gore-tex is a breathable membrane, which allows water vapors to pass through, but does not allow water to pass through.