In analog times, a BW film gave sharper photos because it only had one layer. The same was true for prints (except Cibachrome, and the advantage was gone using multigrade BW paper). Also the color diffusor would make color prints softer.
On the other hand, chromatic aberration will de-focuse the color world when imaged on a plate. Hence a monochrome sensor will not be sharper than a normal one. Three sensors split by a prisma would be perfect and actually, for the first time in photography, would give BW and Color the same sharpness.