Years ago, I worked for NAPA. All major auto parts stores get their starters and alternators rebuilt in Mexico.

Starters are all about the same, check for shorts and replace the selenoid and brushes. Never are the starters rewound. If the problem was in the winding, you'll find out after you install it.

Alternators get the voltage regulator and electronics replaced and checked for shorts. If the problem was something else, you'll find it after it is installed.

The difference is pre-sale testing. At NAPA we tested all electrical parts before they were sold. We had about a 10% failure rate and our customers never had to install a part only to find it was defective, or worse, replace something else assuming our part to be good.

I've never seen Autozone test an alternator or stater before it left the store.

If want to really to be sure, go to the local guy who will rewind the unit if it needs it.

You want to go cheaper, go to NAPA.

__________________
1983 300SD "Guderian"
1987 MR2
2015 Camry
2015 Chevy Spark
2006 Hyundai Tucson