Well, since the tail dock is entirely a cosmetic thing, it shouldn't really play much of a part in a judge's assessment at all. Technically, yes, the length of dock is still written in some of the standards, but a cosmetic thing like that has to be a secondary consideration to actual conformational points. The point of showing, after all, is to judge how well the dog is constructed, not the skill of the surgeon who docked it's tail or cropped it's ears.
What a judge *should* be interested in, with regards to the tail, is where it is set on the dog's back (not too low) and how it is carried. I suppose that if two individuals were in all respects otherwise equal, then a dock closer to the 2" prescribed by the standard should be a deciding factor.
Actual length of dock can be a bit of a fashion thing. But what you should also factor in is that the job of the person handling the dog is not only to show it off to it's best advantage by emphasisint it's good points, but also to disguise it's faults as far as possible

If you had a dog with a slightly long back, for example, one of the things you could do to try to disguise that would be to hold/push the tail upward and forward, thereby making the back appear shorter (and the dog squarer) than is actually the case. Not surprising then that handlers and breeders often prefer a longer dock

Possibly it's also part of the reason for writing 2" as the maximum into the standard - to stop people doing that. It's not that easy to get a good hold of a 2" tail.
Oh - and dewlap is the excessive loose skin that some dogs have under their chin/neck. It's quite correct to have that in some breeds, but not the boxer.