Originally Posted by luis ducoing
I have never used the RZ series of lenses, but to my knowledge the RZ lenses are usually optically the same formulations as the K/L series of lenses for the RB series, and the 140mm Macro K/L is certainly superior (resolution, flare-resistance) to the old C-series lens I use, and posted about here.
So, the RZ 140mm Macro can only be better, you can't go wrong. The one thing the 150mm 3.5 will buy you is shallower depth-of-field, so for typical portraits that would be my lens of choice. But for close-up optical quality, I don't think there is contest between any other lens in the Mamiya line and the Macro, none of them are as highly corrected.
It all thus depends on what you need...