It's been many years since I handled the 119. It is a beautiful knife, with the most comfortable grip of the three, but very smooth, so less secure. I like the thicker, rounded guard and the slight choil, it also seems to have the best sheath of the three.
Of the two USMC knives, I only own a Ka Bar. THe handle of the kabar seems a bit nicer than the camillus and I think the kabar sheath is better. I think the blades are about the same thickness as the Buck, however the extra inch would add some chopping power, although all are a bit light to be considered choppers. Also, the USMC knives have thicker tip profiles, stronger, but less refined - its a trade off. The pommel of the USMC types is probably a bit easier to hammer with.
I don't have any experience with the Buck 420HC steel, however, I doubt its better than kabar's 1095, which is great. the usmc knives are stamped from sheet steel, which could make them weaker than the Buck (if its made by stock removal- but I'm not sure) and the buck seems to have a higher grind and more elgant cutting profile. I've never broken either, and I think on balance they'd be pretty close. How are you planning on breaking them?
The USMC knives have a full length hidden tang, meaning that if the handle broke or rotted off, you could improvise one reasonably easily (not as easy as a full tang), but I'm not sure about the construction of the Buck.
None have a lanyard hole, which is a drawback.
I don't think corrosion resistance is much of an issue in terms of keeping you alive. If you want the knife that will get the most money on ebay when you get rescued, the Buck is probably it. But a regularly used and maintained knife of carbon steel, will work fine for a lifetime, even in a saltwater environment - it might look ugly tough.
If you droped me in the pacific tomorrow and told me to pick one of the three, I'd take the kabar. If I had the chance I'd dremel off the top part of the guard and drill the bottom for a lanyard. Don't forget the next gen kabars, they have some nice options, although for theprice of the D2 one you'd be better off with a camp tramp.