All the knives you listed are good choices. If possible, try to get your
hands on them before you buy them. You'll find one will suit you better
than the others.
Not a deal-breaker on any one of them, but I've found the Gerber LMF
handle to be a bit large for my paw. However, the somewhat rectangular
shape of the handle does give you some good tactile feedback on your
blade orientation that round handles of the USAF knife and the Ka-Bar
don't have.
You might want to add something from the Becker line to your consideration
list. Probably the BK2 (5"-ish blade), based on your other options. The
handles seem a little over-sized and bulky at first, but they grow on you.
And a knife that I haven't seen mentioned here much, but perhaps one
to consider is the Gerber Freeman with the S30V steel. This is a special
production made only for Cabelas. (In the S30V steel -- regular Freeman
are available everywhere, but with a more common stainless blade.) I've
got the folding version of the Cabelas Freeman. That thing is insanely
sharp, and I've read nothing but good reviews on the S30V steel. The
handle has a good feel in the hand too. Normally $109, but I see it go
on sale occasionally for $79. Seems very well built.
http://www.cabelas.com/cabelas/en/t...=froogle&cm_pla=1550202&cm_ite=0027308516498a
Never had my hands on any of the Ontario RAT knives, but they're also
highly respected, from everything I've read.
I doubt you would have any regrets about any of these options. All just
depends which one has the right feel or knife-karma for you when you
pick it up.