Perspective?
Here is my opinion, and not based just on aircraft.
If the auto alternators are new, meaning from the original supplier, then the difference will primarily be features, like over voltage protection.
If they come from X - auto parts, they may be be rebuilt or remanufactured. This can mean a lot of different things, from just replacing the parts to actual checking of all critical dimensions.
Things like rotor balance, class and lubricant for bearings, surface finish of rotor contacts, class of brush material, electrical components, fit of stator in housing, quality of soldered or screwed connections and the regulator type and quality. If you have tinkered with cars, you know the quality of the components and assembly can cause a good design to fail or become all it can be.
If going automotive and want the best probability of success, then a new part made my the manufacturer is the highest likelihood of a long life. Just add the OVPM. Nothing wrong with an owner having different expectations.
If not worried about in flight failure so much, then just get a spare and carry on.
If B&C precision balances the rotors, makes sure the internal wiring is vibration proof, uses high quality bearings with known, specific lubricant, premium brushes and quality design regulator w/OVPM (and I believe they do all that) then the extra $$ may be worth it (to "you") for the value received.
Full disclosure, I have a PP EI60 and will use it until it fails then decide whether to rebuild or upgrade to B&C. A personal choice, not a recommendation.
So, there you have it, (1) cheapest one that fits, get it anywhere, (2) buy a new OEM part, or (3) aviation parts from PP or B&C. Just be sure OVP is incorporated in each selection in some way. Prices increase in that order, but not necessarily the ultimate life.
EDIT: I gotta say, that link posted is a Delco one wire alternator, a very old design, ubiquitous and very reliable in its day. I have that one on my '77 Chevy truck and it never failed. BUT . . I do replace my bearings and brushes every 80k-100k or so. It has lasted for ~260k miles on that truck but is not pulling 60 amps, more like 25A. I have had Bosch and ND last more than 130K miles w/o service, but never a Delco or Motorcraft. At 100k the bearings were dry and ready to go.
