i tend to think of a hatchet as an excellent tool in it's own right. as opposed to thinking of it as simply a small axe. it takes a pretty big and heavy knife to even attempt to keep up with a hatchet in the chopping stakes, the harder the target the more the balance shifts in favour of the hatchet.
there is no way that either my BK9" or RTAK will keep up with the wildlife hatchet chopping hardwood. the're both well convexed. chopping the hard stuff can be down right painful sometimes, resulting in arm numbing shock and a blade flying loose.
that said, a large knife has more cutting edge, better for whacking through brambles, you can baton a big knife to split lumps of wood that defeat even a small forest axe. then there's the durability question, what happens if you damage the eye and or break the hatchet handle? it happens.
so after considering all the options, i realised i needed a hatchet with a solid head and a long cutting edge, or a knife with a longer shock and vibration absorbing handle.