The bulk of the advice here seems to center on the effects of perspective and/or bellows length compatibility.
But the effects of lens length on "style" of portraiture (the process, not the product) are worth considering as well. For some subjects, the more distance between you and the subject, the better; for others, up-close-and-personal is the only thing that works.
To span the range from clinically sharp to dreamily soft with only one optic, the only "modern" lenses seem to be the Imagon and Fujinon SF. It is probably not an accident that for 4x5, they are both 250mm FL. However, my personal experience is that low-key pictures with an Imagon are a good bit harder to make work than those in high or moderately high key.