Just by chance I do happen to own both the Berber Fleece (pullover) and Microtex (shirt/pants).
Haven't really put these to any test. Can just give you my general opinion.
The Berber fleece is very thick, almost shag rug like. I believe that it would reflect light about as much as a shag rug would.. None to little. Its also very warm and comfortable. One of my favorites.
The Microtex is a totally different fabric, as you know. Its quite light weight, and thin. A flat weave much like a regular cotton shirt, but wit a nap. I could see it as reflecting a little more, but surely not much to worry about.
But it is soft and quiet.