I had the SRC brace on my XR600 and never had one problem with the brace or gaurds. the setup is tough and really does work. The gaurd is nice, but if you want something to keep the mud off the fork tubes think about getting that neoprene fork sleeve SRC sells.
The only time I had a problem with the brace was in the lava rock in central oregon. Since the tires would pick up small rocks, then would not fit between the brace and tire. So they would fly off forward in the bike. Never did any damage, just something you notice.
Try the brace, you will like it. About the only other reason beyond looks and USD envy for the USD forks is the lower overhang. But you have to remember that your brake also hang down there with the rotor, so the convential forks give a bit more coverage.
Try the brace! If you ride as hard as I did on the xr600, it was a great investment. It will make riding a lot easier especially if you jump a bit or run into a lot of ruts. It really makes the front end solid.