I was surprised myself and wonder if there is something wrong witn the Wilbers. It is the same spring rate as the YSS but it always felt very harsh to me even with the damping all the way open except for the rebound. Better than stock for sure but not great.
Perhaps the Wilbers is ok on nice German roads but not on bumpy California backroads.
Also the overall build seems very similar on both shocks but the yss is actually designed a bit smarter for the preload setting. It was always a difficult job on the Wilbers due to access.
I read somewhere (not sure if true) that one of the Wilbers engineers left and helped or started Yss.