I was alternator hunting a couple months ago and looked all over internet forums for a consensus on brands.
From reading lots of forums:
DB Electrical used to be considered very good, then around five or so years ago people started complaining that they were going the cheap Chinese route. There are fewer complaints about that than there used to be, so either people stopped buying DB as much, or maybe they improved the quality again since then. China can make quality parts if a company wants them to.
DB does apparently make NEW alternators, not remanned ones. (at least for some models.) Various remanufactured ones from various companies might still have various original parts that might then fail early. So it can be hard to tell what you're getting from a remanufactured one.
Lots of people say get your current alternator rebuilt at a good local rebuilder. Though they rarely ever say how to find a good local rebuilder.
Plenty of praise for Remy alts. They're associated with AC Delco. Which doesn't mean as much as it used to, but it's something.
The dealer quoted me over $700 for a new factory alt. I was leaning towards a Remy reman, but then happened upon a new open-box DB for 1/3rd the price of the Remy so based on how I use that particular vehicle I figured give it a shot.