Usually, the best and easiest way to determine is by looking at the prices: The higher the price, the better the pool. Stainless steel may be the best. But, steel will be affected by chlorine and may rust eventually. Aluminum does not rust. Aluminum by nature is very soft, unless it is an “alloy,” which would make it too rigid for above-ground pool construction. Above-ground pools need a certain amount of flexibility to accommodate water movement and temperature changes. What is also important is to be sure of the gauge of the walls! If the walls are not of at least 30 gauge and have a deep corrugation, (ridges in the wall), they will not last as well.