There are 3 types of Inground Vinyl-liner swimming pool walls. The best is the “POLYSTEEL” swimming pool wall.
Here are the advantages…but let’s first speak about all 3 types of pool walls.
1.  GALVANIZED STEEL wall panel.  Stronger than Polymer-plastic, but they have been knownto rust and corrode.  One must check to see the quality of the steel used, and the quality of the galvanization by a specific swimming-pool wall manufacturer.
2.  POLYMER-PLASTIC wall panel.(sometimes called :Graphex” by one wall  manufacturer). While they don’t rust, they have been known to crack, due to bulging during freeze-thaw cycles here in the Northeast.  They also don’t have the strength of steel walls.
3.  “POLYSTEEL” is a polyester powder-coating, (electrostatically applied and then baked-on at over 400 degrees), over a galvanized-steel wall panel. It doesn’t bulge, rust, corrode, or crack.

“POLYSTEEL” starts with a “CARDINAL” 14 gauge steel-wall panel that is armored with a G235 heavy 2.5 ounce per sq. ft.coating of zinc galvanizing.
Then the entire formed panel is coated and baked-on with a polyester resin, that re-establishes the corrosion resistance in areas where the galvanization has been compromised during the panel-forming process, such as skimmer cut-outs, bolt holes, and cut edges of the pool-wall panel. Remember, with just plain galvanizing, the edges, cutouts, holes, etc. lose their galvanization and that’s why rust starts to form on the plain, galvanized, panel.    Sincerely; Rich DeMarco…www.paradisepoolandspa.com