I have always used brand name fiberglass kits. There are a few but I never used the cheapest . I always found cheapest is just that, crap.
I like using cloth in areas that require some strength. I also will sandwich either pieces of aluminum or steel between the cloth for strength. Matt is good for hard to get areas because you can soak it in the resin and remove the air bubbles then push it into the area.
That's the biggest reason why some matt or cloth will fail...........air bubbles........make sure you force them all out so the cloth and/or matt is see thru. I have always used a stiff bristled brush with the bristles cut back to dab on the cloth or matt to force out bubbles. I have seen guys use a roller and that works but you better get it clean or you use it only once.