I very much doubt that they're different products. I think it much more likely to be the case that they're made from different batches (yes, I am aware that Escalon only processes tomatoes once a year, but I doubt they process them all in one batch) or are filled from different fractions of the batch (at different points in the canning process), i.e., because the tomato pulp is in suspension, the puree at the bottom of the tank will be thicker than the puree at the top, so the puree in cans filled while the vat is full will be denser than cans filled when the vat is, say, 1/8 full; similarly, cans filled with puree from the top of the tank will be less dense than cans filled with puree from the bottom. (While stirring can alleviate this phenomenon to a degree, it cannot eliminate it.) Since the puree in the large cans is denser/thicker than in the small cans, and since intensity of the flavor is a function of the ratio of tomato pulp to liquid, it stands to reason that the large and small cans are filled from different fractions of the batch.
All that being said, I find the flavor of the #10 cans too concentrated and prefer the less intense flavor of the smaller cans. Oh well, de gustibus non est disputandum.