I think a big and heavy knife is a bad substitute for an axe. My reasoning is mainly that the mass isn't optimally utilised.
As a weight comparision, two typical, but different, big knives and a small axe, all with a very similiar size:
As you see, what you need to carry is just a little more with the axe, but more of what you carry is actually used when you chop, and the mass is concentrated further out, also the handle is better for chopping, especially compared with a straight knife.
Some practical tests I've done confirm this. The axe is about twice as efficient as the straight knife, with the khukri somewhere in between. Note that the axe edge is also supposed to be as sharp as a knife edge.
Disclosure: Since I live where axes, rather than khukris or whatever, is what's used in the forest, that's what I'm used to, so I probably use it better than I use something else. It also means I never expected anything but the axe to be best.
I fully understand that sometimes a long edge is useful, for example for lighter vegetation. But then a machete or a parang which doesn't a thick blades is more suitable than a thick bladed knife.
Document created 2000 Oct 22, content last reviewed 2002 Feb 11 by