Here's a kind of Goldilocks situation... I've got three brushes, one boar (A) and two badger (of those, one is almost brand new (B) - the other I got from an antique shop (C)). "A" is VERY stiff, "B" less stiff than the boar, but still has a nice firm body, and "C" is very soft, with VERY little body. What is your preference when it comes to brushes? I've heard a lot of praise for softer brushes - but I think there's a point where a brush is too soft, and kinda useless...
I would break down the issue into two properties: 1) the tip softness and 2) the firmness of the knot (how easy it bends or flays). IMHO the best brushes have very soft tips and moderate to firm, firmness. The best brushes for achieving those properties are well broken in boar brushes and short loft silvertip badger brushes. Not everyone likes the same thing, so don't take my opinion for anything more than it is.
I have a TGN synthetic knot that has super soft tips, but has mucho spine and seems to be a happy medium.
Moderation in all things is not a bad rule for selecting a shaving brush. Not too big, not too small. Not too stiff, not too floppy. Loft not too high or too short. So a brush around 22mm, a badger around 48 to 52 mm loft, with reasonable backbone, is just about right for everything you might want to do with your brush.
I do not like brushes that are scritchy or floppy. When I went to the local brick and mortar store to get a brush, they had 10 or 12 different kinds - mostly Simpsons, Vulfix, Shavemac and Dovo. Some of the better silvertip brushes were soft but still had some backbone. They were pricey, however. The pure badger brushes have backbone but are also scritchy. The Dovo pure badger was the exception. It was reasonably priced, was not floppy, but was almost as soft as the silvertips. Best of all, it was reasonably priced, although I was told that the price has gone up recently. The store now has a completely different brush selection, mostly Frank and one other brand I forget at the moment. After reading that the Omega boar brushes were stiff but had soft tips, I bought one of those, too. It turns out the reviews were correct. It has soft tips, tons of backbone and all at a very reasonable price.
