Do you mean like the insulated composite wall panels ? I believe optimum and radiant both make one with those.
Without a heat source, it doesn't matter IMO. It will slow down the heat transfer a little and maybe buy an extra day with a couple degrees extra. But then in the same token it will take a little longer to warm up as well.
Most of the heat loss is through evaporation anyway, and while any R value is better than no R value, it's still not much with these pools. (Though the manufacturer will claim otherwise and that the walls also cure world hunger).
What I *do* like them for is never rusting. Get one for that alone.