Best type of keel
Keel centerboarders are a good option in the 40 to 50 foot range. (My Dad currently owns a Brewer 12.8 cutter which is a 42 foot keel centerboarder) They can offer good upwind ability with the centerboard down and good downwind ability with the centerboard up. You can partially raise the board to balance the helm and they can be raised to reduce risk of tripping when hove-to in rough going.
Keel centerboard arrangements are not without their own unique problems. They typcially require more maintenance. They can get stuck up by growth clogging the trunk or stuck down after a grounding. They can slam shut in a really bad knock down. To get any real performance out of them you need to play them up and down with the conditions.
In terms of performance, keel centerboarders need to be heavier for the stability as a Fin keel boat. They typically have shorter rudder lengths meaning more drag or less steerage. The centerboard operates in the tip votex of the keel meaning that you need more wetted surface and drag for the same lift.
As to who designed the best keel/ Centerboarders I don''t think you can say that any of the three were always the best. In my mind, the S&S designed Tartan 34 is one of the best K/CB that I can think of. The C&C 41 and 45 were also very good K/CB boats. I am not a big fan of Hood''s K/Cb''ers but that is more about the design of the rigs and their sheer weight which really hurts a K/CB boat worse than a fin keeler.