I love both of these guards. But both of them have problems especially in nogi. Rat guard is pretty difficult to control if the opponent has their arms in, due to the nature of the position it can be difficult to keep their posture down and they protect themselves from the hip bump, unless you quickly go for the wrestlers switch. I have stopped really going for Williams guard/London in Nogi, it's too hard to control especially when the opponent knows the cartwheel pass. There are counters of course, but the main problem with the nogi counters imo is that they rely on the opponent's timing and not your own. I have to concede (begrudgingly

) that Chill dog is far better for nogi than London/Williams Guard.
Also if your interested, I realize i'm a nobody but I have explored and studied these positions quite a bit, to the point where I would be very suprised if I saw something new from either position...
http://forums.sherdog.com/forums/f12...-post-2650585/
http://forums.sherdog.com/forums/f12...-post-2845273/