With consumer scanners you have little control over exposure and have to place your print face to glass. With DSLR you have, if you know how to do it, full control over the exposure and color temperature and is easy to place reference targets for profiling. Emulsion is always up and manipulation and positioning don’t introduce deterioration. A pair of external flash unit are high quality light source. You will need too a repro standing, a spectral uniform medium gray balance card, maybe a rectangular piece of glass or some kind of electrostatic base to make plain the cabinet card without damage, capture in raw, etc.
You can see more here: http://dpbestflow.org/camera/camera-scanning