I have built wood/fiberglass boats and worked with people in the composites industry, so i've had an inside look into this stuff. My buddy's last company built fiberglass and carbon parts for the America's Cup boats.
Chop mat is for fiberglass tubs. Woven mat is for calculated structural applications,(the same concepts apply for carbon fiber). Sonrier is correct about the strength in a single direction, but that is where planning your layers comes into play. You can use 4+ layers at 40*, 90*, and 120* from the original layer in order to resist deflection in multiple directions. The pro's have math and formulae they use to plan out the layout of the layers of glass, I personally just wing it and have been fine. The fenders on the 360 consist of 3 layers of woven 6oz mat at 0*, 45* and 90* and there is hardly any deflection in any direction even when torquing with your hands.
If you're going with a few layers of chop mat, it will work just fine.
Oh and try using a roller with chop mat