The 120 is a lot prettier, buck does a very nice finish on their knives. The kabar is a great all-purpose knife, but the 120 is good as well. If you want to hard use it I would recommend the 5160 version for the tougher steel. However, if you don't plan to chop or split wood with it then it should still hold up really well.
IMO, the kabar is ugly but it is very functional knife. Probably a better knife for "survival" but the 120 is generally a better slicer. Both can take a really nice edge and cut really well though. The 120 has a finer tip making it more fragile but also a lot better for piercing.
I have had both and I use to beat up the kabar as an inexpensive working knife (bought used) and the 120 is use a little but a lot prettier. Eveled mentioned the 119, and that's usually the buck I tend to use when I want a buck or a durable knife with a fine edge.