I cannot speak to the Mustang seats. I have a diamond pattern flat/thin mugello seat and I do love it, BUT it is not 'soft'. It doesn't really have much give or offer cushy padding. The Ribbed seats that you posted visually appear 'softer' to me but I do not know if that is the case. My impression is that mugello can be very accommodating to additional requests like a gel pad etc.. if softness or cushion was specifically a big issue for you. To me, the shape of the pan and foam is a significant improvement to the feel of the original ducati seat either way. I'm thinking of ordering another version of the seat from mugello just for fun to mix things up. The ribbed design is quite nice but they keep showing more and more variety on their Facebook page... lot's of options there.
Someone else will have to chime in with their Mustang seat impressions.