Looking at it just from economics, I would go with a nice badger knot. The cost of a good boar brush is just a few dollars more than what a knot will cost you. You have a chance to make a very nice badger brush for about $10-15 more than what the boar knot will cost you. If you don't care for the badger brush, you can always sell it. I doubt you could get much for the boar brush because even the manufacturers don't. The post on badger types by Joel would point you to a nice best badger knot, and I couldn't agree more, though I do like the boar brushes too.