I think that one of the problems with comparisons is that it depends on the type of device you're powering. I've seen articles (not recently, though) saying that, for example, one brand of alkaline lasts longest in radios, while another brand lasts longest in RC cars. There's also the religious aspect - for years, I would only use Duracells, one brother only used Radio Shack brand, and another only dirt cheap alkalines he could buy by the case (you can guess which brother had the house full of kids).
Since I'd imagine you're thinking about flashlights when you ask the question, I've read HKJ's excellent comparisons (thanks!), and there are a few threads on here comparing CR123As. Even if those threads aren't that recent, I don't think the batteries have changed much over time (and all the American ones are probably the same cells anyway).
If I could find information like what you're asking for, stating that one brand is clearly better than another for a given purpose, I'd act on that. In the absence of such information, the only primaries I use in AA or AAA lights are Energizer Ultimate - that's more because they don't leak, and they work in extreme cold, than it is how long they last. If not for fear of leakage, I could probably keep pumping alkalines through the lights for less money. For CR123A, I use Surefire, because I know they are American-made, rebranded Panasonics. I'd use anything else that met that requirement, so getting Surefires specifically is probably habit as much as anything. Then I keep a bunch of Duracell copper-tops around for clocks and the Zombie apocalypse, and Quantums for things like keyboards and mice.
