I like smaller 2-band brushes. My all-time favorites are my Simpson Commodore X2 (21mm) and my very scrubby Yaqi Sagrada Familia (22mm). I could probably be happy with just these two, but I like travelling with a synthetic brush (usually a Yaqi Sagrada Familia tuxedo), since they dry so much faster. My x2 Commodore was my every-other-day-brush for nearly 10 years, until I rather recently reactivated my membership here and had a RAD/BAD relapse. It's probably still my favorite brush, but the little and inexpensive Yaqi also really hits the sweet spot for me.
Bottom line: Since I like letting my badger brushes dry ~48 hours between uses, and if I were an every-other-day shaver, I could probably get along with just the Simpson X2 Commodore or the Yaqi SF 22mm.
I bought my dad a Commodore X2 in best last summer, so that was my first target, upon starting my own search. He's very happy with it. But after reading what seemed like a near consensus for the Duke for face lathering and for the best all-arounder for under $100 that's where I'm landing (I also considered the Berkeley 46).
I do have a dedicated travel brush (Wee Scot) that I bought before really considering synthetics. Love the footprint for travel, and it performs incredibly for its size. But the drying issue is a consideration. I probably need _two_ travel brushes