I have a Black Fiber, and recently got a 23mm Silvertip Fiber brush, which I'm offering to share in a pass-around. The Silvertip, to me, is everything I always wanted in a brush. It is not only a lathering machine, but has very soft tips, great backbone, excellent water retention, good heat retention and uses less soap/cream than a best badger.
Visually, it is impossible for me to detect a difference between it an a natural Silvertip. I have ordered a 21mm, too.
The pass-around is open now to B&B contributors, and tomorrow I am opening it to all CONUS members who have more than 50 posts.