I'll take a black silicone mask over clear any day. But not because it's softer; because it's better optically, doesn't yellow and even hides the mildew. (Yuck!)
I have noticed sometimes from some makers of the exact same model, that the mask is a bit softer in black than in clear. It's much easier to make a black mask, than one that is crystal (pure silicone) clear.
But... a soft skirt does not always mean good! Often the mask skirt that seals the best has a bit more edge (stiffness) to it. Take our Zeagle Ebon for instance. It's a TUSA Liberator Plus clone... just like a dozen others, but I found that it often digs into a face just a tiny bit more than the TUSA, and frequently that's what the customer needs. And many times they liked the TUSA better. Many Cressi-sub masks also had just a tad firmer skirts than competitors, and often sealed better. Don't take my meaning to extremes, a stiff skirt isn't good, but sometimes soft is also lacking.
(Jees, I can't believe I just typed that!)
Chad