The best portraits are made at a subject-to-lens distance of at least 2.5 meters. I prefer 3 meters. This is due to one essential element—perspective. Perspective is a direct function of subject distance—and no other factor.
As noted in post #2, a 300 mm lens makes satisfying tightly framed portraits on the 4” x 5” format because its focal length relative to the format places the lens at the proper distance for pleasing portrait perspective. To replicate this on the 8” x 10” format requires a lens of 600 mm. A telephoto lens with the required coverage will be easier to use, as it requires less bellows extension. A telephoto requires less bellows because the nodal points of the lens are generally forward of the frontmost element.
Some will argue that a significantly shorter lens is perfectly adequate for portraiture. That may be so for broader-framed portraits. However, they might forget that a tightly framed portrait requires a longer lens to place it at the proper distance from the subject.
The 4” x 5” film records a great deal of fine detail. It can be enlarged to any practical size without loss of quality. It's more practical to use a 4” x 5” camera for such work.