Optically the 120mm MF and 120LS are effectively identical. That leaves several considerations:
- Price (obvious)
- Vibration: If using continuous light the ES on the 100mp makes this point moot. When shooting larger objects (e.g. 16x20" painting) with strobe this point is moot. When shooting smaller material (e.g. 8x10 etching, 4x5 film, 35mm slides) with strobe there may still be slight blurring from the focal plane shutter vibration; most consumers wouldn't notice, but you'd risk not passing compliance standards like
FADGI.
- Vertical hold: The XF (like all SLRs) is not designed with straight-down shooting as a primary use case. When shooting paintings on an easel at parallel-to-the-ground or lean-back-at-30 degrees this won't matter much. When shooting on a copy stand an
iXG or LS is a better option than the MF. If only shooting low volumes this is probably not of much consequence. You can use a rubber band to hold the lens in position but this has several drawbacks (elasticity settling, inconvenience, looks etc).
So in summary if you're shooting mostly paintings, only a moderate quantity, and in a horizontal position, then the MF is just as good as the LS. If you're shooting really high volumes, or on a copy stand, or intend on doing
film scanning the LS or iXG are worth considering.