Oreilly's, I get a discount there, and have always found their parts to be better quality than the already discounted Autozone, my past experience with NAPA has always been that they have to order whatever part that I need.
O'reilly's. Napa is more expensive and everyone I have been to the people working there were total jerks. I'm not building a ricer, so I don't go to vatozone
I haven't had any problems with O'reilly's parts. I have had to replace the alternator a few times but that was my fault and they didn't ask any questions with my lifetime warranty.
Though this is a question about parts, it seems to be keep coming around to employees. I don't know about y'alls geographic region, but I don't particularly care for the knowledge of the people at any of the chains around here. There might be one guy here or there working at an o'reillys or az that seems to know what I'm talking about, but none that are really into the vehicles that I have to work on.
About parts, I always go to AZ just because there is one by my house. I've never had a problem with any of their stuff. I will say, that I HATE oreillys page. There are also very few napa's around here.
As far as parts go, they are all fairly similar and there is a bit of overlap with some of the bigger brand names. I just avoid motorcraft since I tend to have bad luck with their parts.
Keep the wheels turning....dumbest slogan ever, but I work there so thats where I shop (advance), I'm surprised to find out how many swear to me they will never shop at autozone when I suggest there is one down the street if we dont have something.