I've used them all and I always get my best lathers with my Semogue 610, so boar it is. After that would be badger, synthetic, and horse in that order. Badger is VERY close but the boar is more efficient in my use.
Im afraid I cant pick between boar and a badger. I use the badger for bowl lathering and the boar for face lathering if I havnt shaved for a couple of day...... Nope cant pick im afraid.