I own all 3 and the bk9 and rtakII are better than the outcast, just can't get comfortable with the weird handle, it chops well but is useless for light stuff with the full thickness blade.
If you are cutting light branches, berrybush/brambles go for the rtakII as it's point of balance and geometry is better for the scrub and still chops well, a really good heavy machete which Randall had in mind. If you have small hands forget about it because the handle is very large (ok for me but barely)
If you are doing heavy chopping/batonning etc go for the bk9, very comfortable handle and is ok for the lighter stuff.
It really reminds me of some of the heavy butchers I used to use in the slaughterhouse.
Kind of like a 2010 version of the big butcher knifes old mountain men used to pack around.
The little bonus knife it comes with is really useful and fits in an altoid tin BTW
Better sheath on the bk9 than rtakII as well.
The Kabar large bowie is a very underated and overlooked big chopper, I really like it to and is cheaper than dirt..... great sheath. I bring it camping as my beater/loaner chopper/camp knife for family and friends, and was one of my first big knives.
Hope this helps, I used all three this year clearing trails on the 10 acres we bought up north in the Caribou so my opinion is not based on backyard/firewood tests.