Ah-hah, you already anticipated my rebuttal
I agree with you that generally a dog who is bigger at the weight is going to have the advantage. In some case, it can be an almost ridiculous advantage. The old man who rented me a property in TN for a few years, acquired some stock that was unbelievably-huge for their weight ...
and they were naturally long-winded ... and he won a lot of deals with those dogs!
It was almost unfair they were so huge for the weight!
However, that said, my dogs often run a little small for their weight, and yet they win a high-percentage of their matches too,
because they have the intelligence to use their size effectively. For example, my
Mystery bitch was a muscular, squarely-built 38 otc and she faced
Buttercup who was a tall, rangy 38 and huge for her weight. The larger bitch was battlecross that had some serious mouth, but she was also slow and stupid and not quite as physically-strong as Mystery. Now Mystery didn't really have much mouth at all, but she was strong as a bull, very fast, and most importantly she was
a highly-intelligent, pit-wise animal. Both bitches had good air.
The result? That bitch only bit Mystery one time, right across the muzzle at the start, and she did some heavy damage (punctured the bone). But after Mystery got herself out of that bad spot, that bitch never touched her again, even though she was "bigger" for the weight. Mystery got up under the other bitch, deep into chin/bottom jaw, and stayed there the entire time. Mystery was actually up under the bitch (both facing the same direction), with Buttercup literally straddling her back, with Mystery just up under the jaw ... out of harm's way ... and dismantling the bitch's weapons from "a safe hiding spot." Mystery had a lot of experience, and Buttercup was green, so they picked up Buttercup after she started to show she wasn't too happy with what was going on.
The Moral of the Story?: it depends on the style/intelligence of the animals involved. Like a good reach in boxing, that "size advantage" is only good if the shorter boxer stays on the outside and agrees to eat jabs all day. A longer reach can become a
disadvantage in a phonebooth-war kind of fight
So too, having a size advantage can be a great asset to a dog, who uses it effectively, while being smaller for the weight can be a death sentence to an average dog who doesn't have the brains/heart to use what he has in the most effective manner. These roles, however, can quickly be reversed if one style is
smart enough, and committed enough, to use the tools that he has to his best advantage ... which is why
intelligence is such a great trait to have married to gameness
Jack