Mat vs. Cloth… Both have their advantages. Mat is short strands of fiberglass pressed into a sheet randomly. Cloth is woven. For compound curves, mat is the only way to go, whereas large flat surfaces, cloth is very nice! Cloth comes out smoother, but is less pliable.
Then you get into the whole weight issues. Obviously, the heavier the fabric, the stronger it will be per layer, but this comes at a cost. The heavier the mat, the less pliable it is. For large curves, I use 1-1/2oz mat. In the more technical sections, I switch to 3/4oz mat, and double or triple the layers in that area.
Once again I turn to US Composites
. Their mat seems soak up the resin
faster, and becomes pliable faster, and is just all around easier to work with.