I reckon I've got about 15 brushes - badger, boar, horse. All have their strengths and weaknesses. I'm a Yaqi convert now owning two - the bang for buck is amazing. It's fair to say I'm a convert, albeit I won't abandon the old school.
I only buy synthetic brushes now as they work fine and are hassle free. AFAIA the only source of badger hair is the Chinese fur trade and I'm not convinced their animal welfare standards are something I wish to support.