I own a bunch of casket sets and a few convertibles.

Good casket sets: Goerz Pantar, Goerz Doppel Anastigmatlinse, Emil Busch Vademecum.

Not so good: Ralph Golshen 8x10 Convertible Set.

Really not so good convertibles: 8x10 and 11x14 Gundlach Rapid Rectilinear.

If I had to make a bang for the buck recommendation, I would say that the Busch Vademecum set is about the best thing going. It's sharp, surprisingly contrasty, very small and unbelievably light, but the drop in filter arrangement makes shutter mounting a problem.