I look at it this way - I don't go into the woods intending to do a lot of chopping, but I like knowing I've got a tool that's capable of doing it if I need it to.

If I take an axe, all it will be good for is chopping. If I take a knife, it will be capable of a lot of jobs, and chopping is on that list. I'd still rather use a small folding or chain saw for cutting logs, and use the knife to split them. I can split wood a lot more safely while tired or injured using a baton and a good knife than I can using an axe.