G'day! I'm new here, first post, but I kinda like bowies and love the Ka-bar / Becker line too.
I have a few ka-bar and muela including the bk-9 but I don't have that particular muela, but it has been on my radar to collect for a while.
My thoughts are the muela is more a collector's "fighting" bowie, it is made from stainless steel and I have 2 other muela's which are also stainless steel. They are very sharp, very shiny and eh... imho, just too nice to go out and rough up. A lot of muela are full tang but tend to be rat tail, unlike the Becker, where you can clearly see the tang around the scales.
I would be very gentle with those muela, but I'd have no qualms chopping and batoning if I have to on the bk-9. The bk-9 is a proven workhorse. It's just really good out of the box. Some don't like the sheath or the scales but that's easily fixed. The Becker sheath however is better than most muelas, IMO.
Bottom line: I'd pick the bk-9 any day, unless you want just a fighting bowie. The bk-9 can also sorta be put into the self defence role, but I think it primary role is that of a general camp knife, wood processing knife. Order it online if you have to. It's worth it.
If you had to pick a muela I'd go for the 22 - I want one myself!