Hi guys, here's my opinion as an ex thai boxer, ex bouncer, and current Shotokan student (loving it), age 26.
First of all, blocks. The concept is an illusion, it's almost impossible to block a punch, especially against a wicked opponent who can throw punches at different speeds and with/without a delay in some part of the movement. In my best days I was able to throw 8 punches (left right left right...) in 1 second. Who can react 8 times per second? And there's no time whatsoever to do a block. Anyone trying to use blocks in the street will go down very fast. Even against a guy who has no MA training but has experience in fighting.
However, if you mentally prepare yourself, know your opponent is right handed, and you're 99% sure his first strike will be a right hand punch, then you can block and win in a second.
Second, it's also next to impossible to kick someone in the head. It can be done, but with a couple of solid moves to prepare the opponent. If you want to kick a guy in the head, you need to have a perfect instinct - something which you were or were not born with but even if you were, you need to train it before you can use it at all. And you can't do that in kata or in controlled sparring.
Chambering the rear fist...is a perfect way to change the previous paragraph and get kicked in the head.
Street fighting is brutal. No matter how many flying jump roundhouse shots you can do, if you're not a man who's willing to take some punishment, you're down. My point is, karate doesn't teach you to be brutal, not even kyokushin, and mostly you develop an illusion "I can't get hit there, this won't happen, that won't happen". Yes it will. The guy will bite your hand if he sees a chance. No matter how perfect your stance is.
I realised, when sparring against a karateka, it only takes a bit of wit to keep him off balance. Instead of trying to block, move away. Instead of having linear movement (Shotokan), circle around. Strike and move to the side.
As someone said, we're not in some apocalyptic scenario and we're not gladiators. You end up having civilians who can perform certain moves. And the fights are won by brutality, wit and most of all - luck. And karate has a concept that nothing is luck, you "can" control everything. No, you can't.
What I'm really trying to say is - karate techniques are just a weapon. They don't mean a thing if you're not a fighter. But if you are, then your fighting ability will increase. As long as you don't try to block...
So, there's a good point behind developing one's character in karate. That's what matters and that's what makes you a confident guy. Most potential fights can be resolved by posture alone.
And if you already got into a fight, pretend you're weak and sick and then strike full power...with a kiai
Maybe some of my arguments seem contradictory, but that's the way it is. The truth doesn't exist, the world is not black and white, tiny pieces of the truth is all we have. So there's not a definite answer on this subject.
Except that fighting is in your mind. It's an intellectual and a creative effort. So it doesn't really matter which techniques you use, you just need to be able to follow what your mind tells you. I mean, if you know it's logical to grab the guy by his neck but your training routines stop you from doing that, then you've just made an error, and you'll probably pay for it.