Value comes first. For drives and whole setups that means pounds per usable terabyte, and for enclosures it's pounds per bay. After that we look at the specs that decide whether something suits a home setup, which for a drive is mostly the bay rating and how loud it'll be, and for a NAS is the CPU and the network ports.
Specs come from each maker's own page, and every value on a product page links back to it. Failure rates come from Backblaze Drive Stats (36 drive models) and always carry a 95% interval. The capacity figures come from our calculator.
The "who it's for" notes on all 87 product pages come from fixed rules run over those numbers, written a few different ways so the product pages don't all read the same. Retailers can't pay their way into a ranking, and what a shop pays us in commission doesn't come into it.