I installed my VWR swaybar setup last week and I am really happy with it so far.
I think in simple terms, too much swaybar stiffness will reduce inner tire grip while overloading the outside tire. Too little swaybar stiffness will result in too much roll and loss of camber (cornering grip).
My VWR setup is set to soft on both front and rear. Sure, it rolls more, but there is unmistakeably more grip in cornering. It just takes a slightly different driving style.