They might be from the same supplier or 2, but there are still some differences. For example, Centric shoes are GG, while most of the other shoes are FF. The only other GG shoes I know of for these Subarus (FMSI #S676) are the house brand CQ/Wearever shoes at AAP (which are made by FDP), though Centric could also use FDP.
Some drums are coated and some are not. Some have those holes where you can use bolts to pull the drum off the hub if it gets stuck, and some don't. Even if Powerstop and Wagner use the same supplier for their drums, Powerstop is coated on the inside and has the bolt holes, while Wagner has neither.
Powerstop and UQuality could very well be from the same supplier and be identical, so just pick the one that's cheaper (depending on how much RA shipping is to your zip code, people that live in Arizona, Colorado, etc).