Material & Durability: Steel, Aluminum & Heavy-Duty Coatings
Most of the good ones are made from powder-coated steel, and the coating is what does the work. Thinly painted steel starts weeping rust at the cut edges within a season or two, especially near irrigation spray or coastal air. Aluminum skips the problem and weighs less, which is why zero-rust aluminum reels (Gorilla builds a well-known upright version) sell hard in wet climates. Cast iron looks right on a brick wall and is genuinely heavy-duty, though you should touch up any chips before winter. Resin and plastic pots won't rust at all, but thin ones go brittle after a few hard freezes.
Check the hardware too. Makers save money on screws, and a durable bracket hanging on zinc-plated lag bolts will still streak your siding orange.