I've noticed that the earlier Pentax lenses have better microcontrast/resolutions than their later SMC counterparts. This has held true for 50/1.4s, 55/1.8s, 135/3.5s, 28/3.5s, 200/4s with multiple copies of the 50/55/135s sampled. The later lenses may have better macro contrast, especially in contre-jour situations, but I've largely moved my M42 kit away from the SMC or S-M-C lenses for this reason. Macro contrast can be adjusted after image capture, but micro contrast largely cannot (again, in my experience). I haven't experimented enough with other brands to say if it applies elsewhere.

Late model/modern lenses have a look, old lenses have a look.