Keep in mind that this is coming from the perspective of a desert racer
I ran the bark busters, wrap around handguards, blah blah for a couple of races, and I HATED the enclosed feeling with them around my hands. However, the last time I raced, and I was well aware of the possiblity of it, wrap around handguards gave another rider a trip to the hospital, he went over the bars, and both wrists got caught inbetween the bars and the handguards, breaking both of them. I've taken my wrap arounds off, put asv levers so that a broken lever doesn't ruin my day, and put mx type handguards on to take care of roost and brush. For me, with the type of racing I do being a little more wide open, I consider the risk of going over the bars due to a hidden rock in a sand wash or something of that nature, greater than the risk of breaking my hand running into a tree, which if I hit one that hard anyway, the bike's probably going to be fubar'd anyway.
If I rode mx, there is no way in hell you would ever see them on my bike, a lot of mx tracks and series outlaw them.