In the end alot depends on the lens. Over the years have had a lot of experience with Macro and Micro photography on the professional level. Being introduced to this specialized type of photography using a Leitz Aristophot. Around 1990 acquired a Nikon Multiphot system with it's propriety optics.
Macro-Nikkor 19mm f/2.8
Macro-Nikkor 35mm f/4.5
Macro-Nikkor 65mm f/4.5
Macro-Nikkor 12cm f/6.3
Have used Luminars, Milars, and a host of others. None have stood up to those 4 specialized Macro-Nikkors except for one 120mm Leitz Milar I acquired that just seemed to defy the loss of sharpness by diffraction at small apertures... This lens just always amazed me in its sharpness.

Just after the time Digital took over film, I changed jobs/positions, so my experiences were with film but should definitely apply to using a digital back.

Achilles Heal of any copy set-up is alignment of the image capturing unit (film to digital sensor), the lens, and the original being photographed. With the Nikon Multiphot tolerances approach close to O degrees. I've worked a person who set up a copy stand with a Hasselblad H Series Digital Camera mounted facing down visually aligned to the copy stand's baseboard. His results were less than perfect. His alignment was off by a couple of degrees. Even when using a Linhol Heavy Duty copy stand, just by repositioning the camera vertically, alignment can easily be altered.

Have used a MF digital camera mounted on the Multiphot to make digital negatives with excellent results. Camera was aligned. Lens & shutter aligned. mounted the film carrier on top of the Multiphot's specimen stage so knew it was also in alignment. Using the Multiphot's collated light source (large condenser) gave me amazing resolution and sharpness but the tonalities were distorted. Tried using a LED lightbox as a light source and tonalities great but loss in sharpness when compared to the single element condenser. In the end taking one exposure with the Multiphot's collated lamp source and quickly swinging the LED lightbox under the specimen stage to take another exposure proved to work out great. A pain but Digital negs I came close to drum scans. Greatest factor was using the optimum T stop on the Macro-Nikkors to match the reproduction ratio. Fortunately Nikon had published great tables.

Would love to acquire a Phase One for my Multiphot but just can't justify its cost.