I agree. I also prefer Ari's slower escalation to his brother's immediate fury. However, Ari has had a lot more training so perhaps that is it?
I have seen dogs that, when confronted in this manner; just look back, or wag tail, or sniff the ground, get up and look around, and even hide behind the handler.
Just from a hard stare.
(and I am talking about adult dogs' reactions, not puppies.)
I don't like immediate fury either, as that dog is skipping or rushing through the ritual of intimidation and progression of aggression. The whole point of the posturing is to decide who is more "the wrong one to mess with". All these steps (eyes->squaring off and looking bigger->noise->closing the distance->initial physical contact->actual fighting) are all designed to avoid actual fighting as this is advantageous for both parties. And pretty much all animals do this.
Consider people.. someone stares at you from across a bar. You look away and drink your drink, look back and they have maintained the stare. You *will* now feel a threat from this person. You have two options: avoidance or countering. You either laugh and talk to your friend "haha... this weird guy is staring at me", or you counter... stare back, maybe push away from the bar, square your shoulders.. he has the same two options. The next step he counters. You now have to up the ante or avoid. You counter again with noise "Hey, what the **** is your problem with me". He counters with noise back, and begins closing distance to you. You will then have initial non-fighting contact... people will get so close into each other's face that they are rubbing shoulders, or they will shove. After a shove or two, fists are thrown. Dog exchanges are identical save the methods of each step are obviously different.
I don't think its training, I think its just the nature of that dog to progress through much faster... maybe to make his counter more likely to turn his opponent, maybe b/c insecurity keeps him from calmly performing the "ritual".. who knows