My favorite brush is wood with stiff blue plastic bristles. The horses love a good scrubbing with it after a trail ride. A sponge bath and brushing and they are happy to not roll.
I prefer natural for the face, however. Softer
I also go by what feels best in my hands for the back of the brush. I like Oster brushes because the handles really hold up and they are easy to clean. For face brushes I like my wooden natural fiber brush. It fits perfectly in my hand. I've never had problems using plastic bristled brushes and from my experience they seem to hold up a little better.