You are correct, sir!
It is preference.
I prefer badger.
My boar outperforms badgers and the synthetic in my den.
Find what you like best and stick to it.
I have badger, boar, horsehair, and synthetic brushes. Within each group I have some preferences, but I enjoy using all of them. There is no need to stick to one type of brush unless that is your choice.
I have a lot of soaps that vary all the way from soft creams to hard pucks. I find that some types of soaps or cream lather better with certain brushes, so when using a soap, I select a brush that will work well with it. When using hard pucks, I typically select a boar brush. When using a cream from a tube, I often select a floppy silvertip boar. However, some soaps work with any brush and some brushes work with any soap: dense badgers, horsehair, and synthetic.
When evaluating a new soap for the first time, I often use a synthetic brush as it is easier to control the amount of water in the brush.