The texture of that plastic Shocker linked to is rather porous and once dirty, stays dirty.
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Not that I care for the texture of the FRP like you see in fast food joints any better (I don't) but at least it is designed to be easy to keep clean.
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Neither of those plastics is particularly easy to bend either and they're both kinda snap-happy if you do manage to bend them much. I'd also be leery of such brittle materials in cold weather and exterior environments (aka van in winter) combined. FRP is the tougher of the two and I've still busted corners around the walk-in where a leaky freezer door (or one that wasn't closed by lazy workers) got the adjacent FRP paneling too cold, then when the door was finally shut (slammed in anger) the plastic wall paneling broke.
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I've worked with them a bunch in remodeling commerical kitchens/baths (used to own a bar, worked in a bunch, blah blah blah) and if I never use them again I'll be FINE with that.
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They're all tough to join edge-to-edge neatly. That's why you use the trim used for joints and edges. The trim is bulky and traps dirt in its grooves and looks unprofessional in my opinion.