You already have a good understanding of the basic differences. Unfortunately, it will be hard to get more information than you already have.
One reason for this is that mfg's change processes and compositions with no notice to you -- Ozone Swimming Pool's "Superduperexpealidocious" swimming pool walls may have been sold for 25 years . . . and have had 15 different formulations and manufacturing processes.
So . . . the particular walls YOU are about to have installed may have only been sold for 2 years, with the result that NOBODY really knows how long they'll last.
That said, I'd pick polymer. Polymer walls are harder to INSTALL, but if installed properly, will likely last longer in areas with damp ground and regular rainfall.
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