Here is how I look at it for "survival" blades. If you are out camping or in the wilderness trying to live on your own for a little bit, you aren't going to need to be chopping trees. So the big hatchets aren't going to do you any good. You may need something to clear bush with, remove branches, or split some firewood. A decent hand held hatchet works better in this case than any "survival" knife.
The only reason to need a knife style blade in this scenario is to cut smaller things. Like rope. You may also need to skin and clean game. Again, you don't need anything bigger than a nice 4-5" fixed blade knife. Anything bigger is going to be too unwieldy. Anything smaller and the job may take a bit longer.
The next reason to have a knife would be a small utensil knife. Mainly for eating, prepping meals, and perhaps passing time with widdling. A smaller fixed blade or even a decent folder fits this bill. Either one can be used to attach to the end of a stick to make an impromptu spear for fishing purposes. A spear like that wouldn't be all that useful in a defensive scenario. Rather have a .22lr pistol for that in the wilderness. Unless you know you are in bear country, then you might want something bigger.
However, some people like a slightly bigger "chopping" style knife instead of a hatchet. Kukri's work for this decently enough. Again, while they work, I don't think they are the most optimal of setups. A good hand hatchet will do the work a kukri can do for chopping in a faster time frame and easier. And smaller jobs that don't require chopping are better served with a smaller blade. The only reason to get that "in between" big bladed knife is because you are compromising for some reason. Meaning hatchet, small-medium fixed blade knife, and another small knife is just too much to take.