If you like easy splay, then Muhle all the way. The Simpson has tons of backbone and takes some effort to use. Mine is lifted at 54 mm.
Both are really nice but if you want more backbone stick with the Simpson.
+1 The Simpson is far better than the Muhle in my books (in fact I have already offered mine on BST). Only thing is that the Chubby 2 synth knot does NOT feel anywhere near the Chubby 2 badger. It feels more like a deep seated 23-24mm knot.
Thats why I'm eager to try out the Duke 3 in synth (should be more balanced and should make for an ideal travel brush) but at the moment I have too many brushes to think of getting another one...