Based on very little information and lots of intuition reaching conclusions shared by others...
Most "refurb" units are just bought-and-returned products. There's nothing wrong with them. If there is something wrong, it was a problem with a new unit (either broken at purchase or soon thereafter), someone bought it assuming "new" better than "refurb" and got a lemon; the problem is easily identified and replaced with a working part. If something's gonna break, it's gonna break very near the time of acquisition (or near predicted end-of-life); few breakages happen during the middle 80-90% of product life.
New machines are cranked out in a factory en mass.
Refurbs, most of which are either undamaged/new or lightly/obviously broken, are individually inspected with the keen awareness that this particular unit may very well have a particular problem. They receive more attention from better trained inspectors, and with more...domestic sensibilities. Then they're put thru the same, if not greater, QA testing as the factory provides.
So, at the risk of the occasional abused machine with deeper chronic problems, most refurbs are in effect (if not actuality) new units with an added layer of real-world testing, individualized attention/correction, comprehensive re-testing, all done within local cultural norms. And you get all of that not at added cost, but at a discount off the original price.
So the theory concludes (again, just hypothesizing with little knowledge of what really happens) that the refurbs are the most reliable and/or best value.
Let's put this to bed. Returns and refurbs alike are binned into lots of, say, 50 units. Third party repair companies bid on them. The winner takes possession, runs triage according to apple protocols and apple diagnostic tools, performs any needed repairs out of pocket, and then places them up for sale linking in to Apple's web store. The products may also be sold in-store.
Any purchase of a refurb is fulfilled from the repair shop with generic packaging. Warranties are reset to day 0. The end.
Oh, and scuzzy remanufacturing shops will sell the truly fucked unrepairable gear in-store and try to pass it off as new. Get caught and Apple will annihilate you.
Most "refurb" units are just bought-and-returned products. There's nothing wrong with them. If there is something wrong, it was a problem with a new unit (either broken at purchase or soon thereafter), someone bought it assuming "new" better than "refurb" and got a lemon; the problem is easily identified and replaced with a working part. If something's gonna break, it's gonna break very near the time of acquisition (or near predicted end-of-life); few breakages happen during the middle 80-90% of product life.
New machines are cranked out in a factory en mass. Refurbs, most of which are either undamaged/new or lightly/obviously broken, are individually inspected with the keen awareness that this particular unit may very well have a particular problem. They receive more attention from better trained inspectors, and with more...domestic sensibilities. Then they're put thru the same, if not greater, QA testing as the factory provides.
So, at the risk of the occasional abused machine with deeper chronic problems, most refurbs are in effect (if not actuality) new units with an added layer of real-world testing, individualized attention/correction, comprehensive re-testing, all done within local cultural norms. And you get all of that not at added cost, but at a discount off the original price.
So the theory concludes (again, just hypothesizing with little knowledge of what really happens) that the refurbs are the most reliable and/or best value.