I bought the Marston mats (punched aluminum) as it was easy to create angle slides to fit under my Front Runner roof rack, the Matrax would not fit and I wanted to carry them full time. Not so much with MT and I did not trust how much the UV might degrade them.
As far as durability goes, I can reshape them (can't reshape broken plastic) and they make a great table or even seating if none is available. The guarantee is no good to me if I break the plastic far from home and can't use them.
Can't sit on MT.
I have both and the ones that are always on the truck are the MaxTrax. Been on the roof for four or five years and UV does not seem to be a problem, even in southwest desert. If UV still worries you, just spray them with a coat of paint that bonds to plastic, same as used for PVC pipe that is exposed to the sun (think pool equipment pads). My other planks are pierced aluminum. MaxTrax seem better for bridging than are aluminum. Steel probably the best but just too heavy and unwieldy.