Well, the chart (18464_1) shows mud, and I have had trouble with my Manson Supreme 25 setting and holding in mud. I think that its shape is optimized for grass, rocks, etc., and it plows in mud, just like a CQR. They advertise "It's Spear Head means that weed isn't a problem for the Supreme." That spear head probably goes right through soft stuff.
I do notice that Manson now has a Bruce copy and they claim "The Ray anchor is a quick set anchor. It's ideal for use in sand, and mud. It usually sets in just the length of the anchor itself."
I do plan on using the Supreme in So Cal because of the seaweed/grass and rocks, but I went back to the Bruce for mud this summer. Just more cross sectional area to pull through the mud.
I think they're both fine anchors, just use each where appropriate.
Boris