I have a 2-band and a silvertip, both 24mm knots, and both great. The 2-band is actually one of my all time favorites. The Silvertip has quite a glue bump, but works well nonetheless, doesn't splay too much.
Oh, and the best thing about these brushes, they were very cheap, about £11 for the 2-band and £16 for the Sivertip, which makes me love them even more.