Yes, the tessar construction of the M can potentially have higher contrast than the airspaced 4-element dialyte construction of 450 M Fuji; but a lot has to do with how well shaded the lens is, and how resistant the inside of the bellows is to flare. I use both Nikkor M's and Fuji A's and C's for color work as well as b&w, and the contrast distinctions are rather subtle. By far the most contrasty lens I ever owned was a multicoated Kern 14 inch Dagor, with its only 4 air/glass interfaces. It was so contrasty that it was problematic for color chrome shots, so I replaced it with the single-coated version instead.
Regarding bellows flare, for example, I discovered that the standard Sinar 4x5 box bellows is much more susceptible than the earlier Norma tapered bellows when the huge image circle of the 450C came into play under certain circumstances. But in its more routine use for 8x10 format, that has never been an issue so far. I only use the 600C on 8x10, and have never had a flare issue with it; but then, I intelligently strategize the use of all my lenses, especially when pricey 8x10 color film is involved.
Of course, a good compendium shade helps a great deal because bright reflections can come from the foreground, and not just the sky, especially in mountain scenes with bright snow or ice or glacial polish in the foreground, or in the desert with bright playas.
