They are both warm copper alloys with different character. Brass, copper and zinc, is brighter and more golden and takes a high polish, so it suits refined interior railings. Bronze, copper and tin, is warmer and browner and weathers to a stable patina, which makes it the traditional outdoor choice. In Bellevue we tend to use brass for interior statement stairs and bronze for exterior and architectural work, and we will guide you to the right one.