I think you have your focus backwards. Usually you buy a boat and the keel sort of just comes with it. The only relevant questiosn for a keel should be driven by how much shallow water you must navigate: centerboard, shallow draft, deep draft. I personally feel that shallow draft choice(whether Scheel or wing or just short )is a worse peformance compromise than a centerboard. Decide what water depth meets your needs and pursue models with that configuration. In general deeper is better!