To my surprise, when I used a Becker Brute as my main chopping blade on a two-week wilderness survival video shoot, the handle became tackier when wet instead of slicker! I never had a problem with grip or sliding up onto the blade even once.
I also have, and really love, the RTAK. The handles on both are good for bigger hands. I like the RTAK handle better, combined with the balance of the blade. I have a BK7 as well, but not the BK9, so I can't compare overall performance between the two. But I've held the BK9 and swung it around to get a feel -- great knife. For lots of brushwork and clearing, the RTAK has it over the BK9 hands down, tho, because it was designed to be a combo of machete and survival knife, mostly for jumngle environs. The balance and lighter blade make it less fatiguing to hold if bushwhacking through dense jungle. The handle is somewhat machete-like as well.