When I am in the jungle I will carry a machette. I have destroyed machettes on hard wood in the past with ease, its the wrong type of blade for northern climates.
As far as survival goes it is subjective what size of blade. Some feel a small Mora is fine and some like a 10 inch chopper. To put it mildly this is a LOADED topic as people are pretty passionate about their blades.
I will break down my thoughts by starting with what and why and where.
I am of the larger blade is better for survival purposes camp because it is a more utilitarian piece of gear. A shorter than 7-9 inch blade is fine for cutting and thats about it. For survival purposes you will have the need to chop trees or limbs greater than an inch in diameter. Unlike others I find a 7.5 inch blade about perfect for chopping smaller trees and isn't too big to be a pain to carry.
Many of us carry a saw and yes it is faster to saw a 3 inch tree with a saw but when limbing the tree of branches a longer blade more than makes up for the saws speed cutting the trunk.
Splitting firewood to get at the dry center is a pretty important skill in very wet weather and does make a big difference in getting a good fire going. A saw cannot do this in any way. A saw blade cannot cut anything that requires a sharp edge either. A short blade cannot be pounded through thick logs.
It is this one exercise that separates cheap knives from good ones and makes longer blades the choice for me.
Yes, you can combine a smaller blade with a saw and do ok but you will never do this splitting action with that saw blade combo. Anything short of a hatchet and this is not possible, unless you have a good 7-9 inch blade. A hatchet also weighs a lot more than one large blade and is less utilitarian. As far as folders are concerned, they ARE NOT meant to be beat on and thus not a true survival blade in the truest sense of the term. There is not a folder in the world that can take this punishment and nor should it, they are not designed for it.
If you never plan on being in terrible weather when the woods are 2 weeks soaked with rain then forgo the large blade. If not then splitting is THE ONLY way to find dry wood that could make a life and death difference. It is this demo that sells my students on the virtues of large blades if for no other reason.
Do I carry a 7 inch blade backpacking?
No as I am mostly on trails and carry a shelter etc... A lower exposure to risk.
Do I carry a large blade when a situation is unknown and my exposure to higher risk and nasty situations is great?
Damn right!
SOme Busse products in proper use.
Large blades are prefered if you have experienced their utility.
In conclusion I will say for many a large blade is overkill unless you believe you may be in the right situation or have need to split wood for fire,which in my opinion is very likely. There is no hard and fast answer you must make your own choices as to what you want to carry and what needs you have to cover off with good tools.
If I had $300 to spend it would for sure be a Busse product probably used and 7+inches in length, they can't be beat for quality.
My 2 cents.
Skam