Usually I find a longer blade, anything more than 4" or so, to be tiring to use for production work. Even with a smaller knife I often find the bulk and weight to be burdensome. For a long time I carried a SAK, a Tinker, in my pocket for EDC but it started to annoy me. I switched to a much smaller and lighter Shrade single-blade knife that has a blade about 3" long. It did about 95% of the same jobs without being annoying or making it look like I really happy to see the ladies.

General consensus if in favor of larger knives but it has to be noted than our distant ancestors clearly skinned and butchered woolly mammoth with a stone knives that were only a couple of inches long. Some experts claim most working blades of the time were an inch long or less.

A knife should cut well. Sharpness is up to the user so saying a knife is sharp doesn't mean much. The metal should be soft enough to sharpen without having to use special equipment but hard enough to hold an edge so you aren't spending all your time sharpening. Also tough enough to take a moderate amount of heavy use and outright abuse without dimpling, chipping, or breaking. Forty years ago you had to spend real money to get an acceptable quality stainless steel. It is pretty hard to find a knife over $15 that doesn't have a usable level of metallurgical quality.

It should also be light and compact enough to make carrying it a insignificant burden. Rambo-sized knives tend to get left at home because their size and weight make them a burden for most people. Life is simply too busy and tiring to spend energy schlepping around a knife which is sized for the largest job you can imagine.

Most survival uses can be handled by a small knife. It is only when you get to fighting grizzlies and splitting shakes that a large knife shines. The first is pretty much optional, not to mention foolish, The second is homesteading. Survival is getting out of trouble. Not setting up housekeeping.