Fixed vs folder is a common discussion among tactical guys (the real kind, not mall ninjas) at beer call after work/training. Opinions vary, and the science is definitely not settled!
Now, I'm not particularly concerned what you carry for mundane tasks like opening packages, trimming wires, cutting off a piece of sausage, etc... y'know, the stuff we all do with our EDC blades. For that, there's not a lot of argument either way other than your personal comfort and preference. But for serious applications, most guys prefer fixed blades.
The gist of it breaks down like this: if you get into deep enough fecal material to be resorting to a knife for fighting, you are in a real bad world of fecal material. Under those circumstances, the less thinking you have to do about it the more likely you are to survive. Note that I do not use the word "win". So in those circumstance, having to open a folding knife with one hand that might already be injured or bloody may be a non-starter. So most tactical guys I know carry a fixed blade, and often more than one.
The Ka-Bar TDI is one that a LOT of guys carry on an EDC basis, strictly for serious social purposes. I have one that I used for EDC for years, but I gave it away to a needy guy from a foreign land and haven't got around to replacing it. Carrying a deep cover knife like the TDI in addition to your EDC clip folding knife makes a lot of sense.
