Copper is naturally antibacterial and antimicrobial, killing most bacteria within hours, which is a major selling point for hygiene-conscious buyers. Additionally, copper has superior thermal conductivity, meaning the bathtub will warm up quickly and keep bathwater hot for significantly longer than acrylic or cast iron alternatives. For aesthetic longevity, confirm if the tub has a living finish (natural patina) or a lacquered seal; the former heals its own scratches over time, while the latter maintains a constant shine.