A big plus for a lot of us older guys is the lower weight of aluminum molds when talking more than double cavity. A lyman 4 cavity is heavy and RCBS are double cavity so your only option if you cast a LOT of bullets are LEE, NOE or accurate, and these are AL molds (brass too but have never had one). Properly used and cared for AL molds will last a long time and produce a mountain of bullets.