If you are doing anything that involves exertion and a lot of movement, the thinner fleeces with Lycra (Like Malden Mills Powerstretch) are a good choice. Powerstretch has one fleece face and one knitted nylon face that makes it easy to layer. I have a couple of Patagonia pieces that date from the first introduction of Powerstretch about 15 years ago, and they're almost like new. There are many newer variations on this concept.