Interesting post, ajasen...
This is a topic of conversation that has come up numerous times within my group of training partners, as well as among the doormen/bouncers I worked/trained with.
I find the biggest problem with pro/con articles and debates is that they are exactly that: too black and white. There is no room for middle ground/situational discussion. This becomes glaringly evident when discussing fights, and especially when discussing "streefights".
First off, anyone who has ever been involved in/broken up/run from/had to deal with a "streetfight" will tell you that they are completely unpredictable once they begin. I say once they begin because there are often a multitude of cues that will let you know when something is "going to go down". This unpredictability (IMHO) is what negates the relevance of a "who does better" argument. The best trained ringfighter/martial artist in the world can't do much good when his opponent's drinking buddy sneaks up behind him with a barstool (and I've seen it happen), just as the most seasoned "streetfighter" probably isn't suited for a BJJ Blackbelt suddenly working him into a triangle choke.
The idea of who does better is completely dictated by situation and circumstance. Will the ringfighter/martial artist be in better physical condition to handle a fight? Probably. Will the streetfighter be more likely to break a bottle over your skin? Probably. But how will either react to a sudden change in fighting syle, position (like "Oh cr*p, how'd I end up pinned in a corner?"), or number of opponents? Totally unpredictable.
You wrote two things which I find very relevant:
1) Fear makes a tremendous difference!!
2) The streetfighter, I assume has a much better handle on the adrenaline scenario.
Fear is most definitely the great motivator. And it comes hand in hand with its good friend...Adrenaline. Ultimately, it is what you do with the fear and adrenaline that makes the difference. A trained martial artist can freeze up, just as an untrained bar customer can go hog-wild and tear up a bruiser that outweighs him/her by 100 pounds. I don't know if I necessarily agree that the streetfighter has a better handle on andrenaline. The ability to start a fight is often the result of fear and adrenaline, while the ability to fight well or end a fight is often dictated by the ability to control your emotions or physical reactions to adrenaline.
I'm not personally convinced that a person that enters willingly into a violent scenario on a regular basis (and I mean bar brawl, or street fight, not heavy sparring) is necessarily better at handling their andrenaline dump. I am convinced that an individual doing so is more likely to have a history severe emotional problems or even borderline psyopathic tendencies.
In order to function efficiently when placed in a violent situation (which is hopefully a rare or nonexistent circumstance) it is essential to not only train under stress, but to recognize your bodies reaction to stress and act accordingly.
As Bruce Lee said: "There is nothing better than free-style sparring in the practice of any combative art. In sparring you should wear suitable protective equipment and go all out. Then you can truly learn the correct timing and distance for the delivery of the kicks, punches, etc. It is a good idea to spar with all types of individuals--tall, short, fast, clumsy. Yes, at times a clumsy fellow will mess up a better man because his awkwardness serves as a sort of broken rhythm. The best sparring partner, though, is a quick, strong man who does not know anything; a madman who goes all out, scratching, grabbing, grappling, punching, kicking, and so on."
In closing, my hope is that the last thought on anyone's mind in a fight is: "I wonder if this guy/girl is better at handling the adrenaline scenario". Either run, take care of business, or call over the big guy in the security shirt.
Hope that all this rambling made sense...