Here's my grade book for thrift stores. I know results may vary based on area, but this should be general overview. Also until I actually looked, I thought we only had 2 thrift stores in my area, we actually have about 20.
(F) Insert Name's Thirft Store, Usually run by two types of women. One that collects bric a brac/ knickknacks/ various figurine trinkets as well as old old overpriced junk. Like a Pentium II 466 mhz computer with a yellow monitor for 500 dollars. The other type, a on the cusp of being a hipster but too old woman that has various higher end items at high prices. You could likely see a Nintendo/Super Nintendo for sale with a Mario title inside. This too would also be overpriced because it has been hipsterized. These are worth going into once or if you are bored, twice a year.
(C) Goodwill, these are everywhere. Usually the size of a small supermarket (big for a thift store) these are best if you are looking for clothes. They have a very high turnaround of inventory. So you are looking for games, etc, you gotta get them within an hour or two of of being put on the shelves. The goodwill here routinely has a line outside every morning. With the exception of the line, this has been the same experience that I have gotten at every single one in other areas.
(C+) Salvation Army, Similar to goodwill but with more ghetto inventory. This could be because of the various discounts that people can get. Seniors, Students, Government employees, (Wednesday)
(B+) Hospice, This place in my opinion benefits from having a specific cause. I assume companies can get tax breaks from donating here, as I see various dumps of specific types of items. Motorcycle Gear, Old Dell/HP's with desks. This place also gets a lot of antiques, maybe from families/people under hospice donating there own items. This place is more expensive on their clothing and antiques, but has a general price for games 1.99. This likely keeps a lot of ghetto people from going, as I normally just see old people and hipsters buying clothes.
(A-) Humane Society, Also imo benefits from having a specific cause. The one here has a old man that comes in every now and then and rights them a donation check sometimes of upwards of 35,000. Many Animal lovers come here for pet supplies and thus also make their donations here. A lot of nice items come in usually from people clearing out their house.