In cloth, the fibers are bidirectional, as in they only go side to side, and up and down in a weave.
Mat Fibers are non directional, they go every which way and are not alligned.
Cloth is easier to work with as it does not spread and frey like mat.
Cloth will be harder to work into tight bends and complex corners.
Bidirectional cloth will not be as strong as the mat when both are correctly applied... maximum strength, use both, alternating layers.
For these used here for armor applications, if you are not expereinced with fiberglass aplication, just use cloth...
This if for pep helms by the way, laying up fiberglass in a mold is different if you would like to have a quality product when done.