The XXXX was originally developed for sponsored athletes to use in really big mountain(read heli,Alaska or backcountry). The first ones were 198s and used DH constuction. When the red and black(darth maul graphics) came out there were two versions in 186 and 195(going from memory here). The 186 used isocore (microcell on steroids)in a traditional construction. The 195 was again DH based, both had twin tips and evolved into the current XXX, with the same sidecut but construction differed from the XXXXs in that they are way easier to ski and better suited to a wider cross section of the skiig public. The current XXXX is a 195 and is very wide with about a 45m turn radius. In Canada the have the same graphic as the XXX but with Hugo Harrisson Team Rider graphic around the Xs on the tail.
Having been on them, and seen really good skiers ski them, if they haven't been offered to you, you probably don't need or want them. I only got to ski them because I mounted them and I will stick to regular XXX thanks. Even some of the cliff jumping super freaks feel the same way, they need lots of weight or lots of speed to work well.