When you’re out hiking you need some kind of cutting tool, even if it’s just a small pocket knife that’s better than nothing. A blade will keep you alive in the woods as you can use it to make anything you need to survive. The question is, if you have to choose should you bring a straight Knife, A fold-able saw or a standard multi-tool style knife (like a Leatherman or Swiss army knife)? All these tools have pros and cons so the choice is one of preference and experience, some people (with enough skill) can even get away with not having a blade.
This one is the most difficult but if you have skill you can make your own edged tool while you are in the woods. This will help save weight (as you can leave the tool when you are done with it) and is pretty impressive. Stone tools were used by humans for millennium and make a viable alternative to a knife if you know what you’re doing. I don’t know how to make one of these with any reliability but I have seen what they can do (you can make an ax, knife, spear and more) so it would be a handy survival skill to know.
This is my choice. I will take my ka-bar knife over any other tool. You can chop wood, use it to hammer, split logs, cut line, fashion other tools (emergency tent pegs made out of sticks saved me one time), and the list goes on. This is a tool that requires some skill to have it replace what a multi-tool can do though. It can do a lot more than a multi-tool but a good knife can be expensive and they tend to weigh more. This is my preference but my partner prefers a multi-tool so there is nothing wrong with not being a fan of the straight knife. Even I have to admit that sometimes it’s nice to have a pair of pliers handy (with the multi-tool).
I would class a folding saw or ax as something that is nice to have but should not be a replacement for a knife. Some people are masters with an ax or saw though and I’m sure they would argue against me here. Once again it comes down to your skills and your preference. If you’re going to be cutting a lot of wood a saw or ax will save a lot of energy. I always bring one when I go on canoe trips and have to admit that it is much more pleasant to use a saw than to hack away with my knife. I wouldn’t try to survive with just a saw though but you could, any blade is better than no blade.
This is the one I think beginners should use. A good tool will have a saw blade, a knife and a bunch of other stuff (that you often end up never using). It is a good hybrid of all the options and will help you in deciding which you prefer. It tends to be a jack of all trades but master of none kind of situation with these but that’s not a bad thing. A multi-tool is also light and durable so if you are trying to save weight these make another good choice. I used to carry one when I first started using just a knife, they are always nice to have (but my knife eventually replaced mine).
Like most things when it comes to hiking and camping this is a matter of choice and preference. The only way you can figure out what works for you is to get out there and start experimenting on shorter hikes. Start with a multi-tool and see if that’s all you need or if you would feel more comfortable with a knife or other tool. Remember though, that unless you know what you are doing, a blade of some sort is a necessary tool in the woods, with sharp steel and skill you can survive indefinitely.