I'm certain back in the early 70's when the v.3 was the latest, it was considered by many to be the top gun because of better contrast and simpler close focus, although the rigid/DR was still considered slightly better for central resolution despite it being present with very low contrast in exchange for high resolution. The DR also benefited with an extra 8" or 9" close focus. My experience with every version I've used from the DR to the current version is that each succeeding formulation improved contrast and resistence to veiling flare in adverse lighting. Full aperture IQ improves about 1/2-1 stop with each succeeding optical formula. Back to your original question, v.3 is the odd man out because the tabbed/current version is optically a little better (especially in the outer field) and the Rigid/DR trumps all in build quality, central resolution and it's medium contrast is favored among many B&W film users. I've used every version and the black Wetzlar (v.3) was my absolute favorite in terms of ergonomics, not to mention extremely pleasant image rendition, possibly the best of all the designs in that it still retains a vintage look but far better sharpness than early lenses. The new current version is a little sharper across the frame but sacrifices some of that vintage fingerprint.
