As I drink vodka almost exclusively, and Tito's almost exclusively within that, I'm going to try the Kirkland label. That's right up my alley.
As for name-brand vs. signature, El Barto has it right, I think. They cut corners elsewhere, and there MAY be some differences with the product itself. I know that working for an electronics manufacturer, we used to supply product for off-brand use. But it wasn't EXACTLY the same. Let's say that the product had to pass a certain spec - let's say it's got to be rated a "2" on a scale of one to five - to sell it. So all 2's or better would be sold, everything below that was scrap or rework. Stuff rated 5 would be our military or government contract stuff. Stuff rated 4 or 5 would be our name brand stuff. Stuff rated 3 would be the off-brand stuff, and stuff rated 2 might go to discount parts distributors.
Put in terms of potato chips, 4 and 5 would be less than one "brown" chip out of 100, and of a certain size. 3 would be 1 to 5 brown chips per 100, and of a certain size, but with an allowance for smaller pieces. 2 would be 5 to 10 brown chips per 100, and of a certain size, but smaller still. We did this with lightbulbs, for example. For vodka, there might be a purity standard. Doesn't mean your vodka IS less pure, but maybe the consistency isn't QUITE the level of that which gets poured into the Tito's bottle. It LIKELY is, but not guaranteed.