My Royal Balls actually broke on me, but that was my own fault--I stored them in the same box as butt plugs of indeterminate material, and the butt plugs actually started to eat through the Royal Balls. =/
That being said, after I pitched the plugs and the Royal Balls and picked up the Smart Balls, I would never go back to Royal. I found the Smart Balls jiggled more and were more fun, look prettier, and since the string can be cleaned as well, I don't worry about hygiene or anything.
Smart Balls for the win!