The answer to your question is, obviously, "yes", as you can generate an infinite variety of b&w renditions of your colour image, but the only thing that you can vary with the b&w one is the local and global contrast and exposure; you cannot lighten or darken specific colour ranges only luminosity ranges.
That said, the b&w Leicas will produce slightly cleaner / less noisy pictures than their colour counterparts (particularly with older lenses, which were not corrected in the blue spectrum, because film was not sensitive to it).
How much any of this matters depends on what you are shooting, in what volume, and what you intend to do with it and how good your post-processing skills and aptitude are.