Okay, since the UFC seems to be the end all be all of martial arts to you folks...
I currently train systems that utilize knives, swords, and sticks. I am only a beginner in this system, granted, but I think there's a good chance I'd win a fight against even the best unarmed UFC fighters. There are totally unskilled people who, given a weapon, or just a different opportunity, could do the same. I think there's also a very good possibility that people who have trained my system would have a much higher survival rate against me in such an unfair, unarmed vs armed fight.
I'm not even sure that the best UFC fighter in the world would necessarily win against an average practitioner of a given weapons based system if you give him a weapon. Sure, he may have a physical advantage and good reflexes, but he has absolutely zero experience, knowledge, and muscle memory.
Does being the best UFC fighter in the world also prepare you to do any of the following?
1. Hit someone without gloves, and not break your hand
2. Take someone down, and not have your head kicked in by their buddy
3. Deal with multiple opponents
4. Handle both trained and untrained opponents who are much larger than you, and who behave very differently than they do in the ring.
5. Handle a variety of weapons, including sticks, knives, swords, or even firearms?
6. Deal with an attacker who may be wielding any of the above variety of weapons.
7. Make most efficient use of bodymechanics and techniques given the very big changes that subtle differences make when wearing clothes, shoes, lack of training gear, and the potential for weapons, multiple opponents, and all other factors mentioned here? People really under estimate how much of a difference small things make. *Really*
I'd also argue that the way people behave in a non sportive combat environment is very different. Committed, unskilled attacks are not always as easy to defend from as people think, and always practicing against uncommitted, skilled opponents sort of robs you of learning what you can do in response to them. Ending a fight is all about efficiency, and taking advantage openings that your opponent gives you while not getting hit, stabbed, or cut yourself. If you don't train versus a wide range of attacks at various distances and with all sorts of implements, your performance will be suboptimal for the situation.
My argument is a case for being
unspecialized. Competitive fighters must specialize highly. On the other hand, people with a more general approach to preparedness and combat must specifically avoid specializing and adopt a general approach that can deal with a much broader spectrum of threats.
Let me just give you a very tiny example of how specialization hurts: In Filipino Martial Arts, most people train with a light weight rattan stick of exactly 28 inches. However, the moment you pick up a fighting weight stick twice the weight, or a stick that is a little longer or shorter, or indeed a blade or machete, things become extremely awkward if you haven't handled that specific length, weight, and shape or nature (blade versus impact) weapon before, and the nature of what you can and can't do with each one changes a lot more than you would think. If you always train with that one implement of a certain size and weight, I'm sure you can compete well in a stick fighting match. But you will be far less effective when wielding anything other than that 28 inch light weight rattan stick that you spend all your time training with.
Then, there's the nature of the sportive context in which you test your skills. Some people treat the stick as a stick. Some treat it as a blade. Others seem to totally ignore what would be, without protective equipment, lethal shots to the head and rush in for to grapple or take down, which I can't really understand. Decided norms around competition hugely affect how you test your art, and who would come out on top if you were competing.
That's just an example of minor differences, and applies across the board to things like wearing or not wearing gloves, etc.
Then there are things you simply don't train for at all if your focus is purely on competition, such as multiple attackers, hitting with your bare hands, dealing with weapons, multiple attackers, concrete, and all sorts of uncertainties which do not just change what you do a little bit, but completely.
I just watched a video of two trained, very competent sports fighters get into a street fight with a larger group of random people. They did really good, until one of the random guys picked up part a large piece of construction lumber laying around, and swung at one of them. Not knowing what to do, his natural, trained reaction was to back off and try to get out of range, and he wound up getting hit squarely in the head, knocked to the ground unconscious, and stomped on. You can say all you want that "oh, I know better than to do that" and "I can deal with X or Y" but until you've trained to do so and have ingrained and make it second nature, you had better think twice about whether or not you can, indeed, do what you say you can.