I collect "survival" knives. Most have a 4" to 5" blade. I suspect that the reason for the size has more to do with ease of carry than performance. Personally, in the terrain that I go into, a 10" to 12" blade is more my speed. I can do a lot with a camp machete or DFLE. While not ideal, you can use a large knife for small jobs, but a small knife doesn't make it for the big jobs. Going into the swamps without a big knife is like going into the North woods without an axe. The Scrapper 6, ASH-1, M6, SARsquatch, Ratweiler, Chopweiler, NMSFNO, and SOD make sense as survival knives to me. They're big enough to be useful and small enough for easy carry. But I still prefer a longer blade. Give me a M9LE and a multi-tool or SAK, and I would be set.