There is no RZ67 wideangle sharper than your 65 M-LA; if you want better then you need to save up for a Mamiya 7. The 50 ULD is pretty close or on-par though and is of course wider. Once you reach f/11, they're all (except non-floating wides closer than a couple metres) basically the same in performance; stopping down makes even the poorest lenses look decent. If you stop down to f/22 or lower, it doesn't matter what lens you're using because you will be diffraction-limited and that is a function only of the aperture. Though shooting at f/32 will give you lots of DOF, the results will be visibly soft with any lens.