With the 5DIII, full auto isn't an option anyway, due to the Canon SDK you have to set the AFMA values yourself - so in that case, I'm not sure there's too much benefit to the Plus version over the Standard (although the Plus gives you manual mode, so you can shoot all your images then analyze them later in FoCal - that's what I do with my 1D X). I have the Pro version, which offers a range of additional tests (focus consistency, testing all the focus points, lens aperture sharpness test, etc.).