I think garage sales are better than either. You can find lots of deals on things, most are things you use & need. I love finding a rummage for my dd's clothes especially ones that are reasonable & or are just getting rid of things. Occasionally you find ones where they sell it all for .25 to get rid of it.
I love those folks! My aunt even found a brand new w/ tags on winter snow suit for .25!!!!
I swear some of the subdivision rummages were being held so they could pay their mortgage or something! *LOL* I'm not paying $3 for a used tee from k-mart!
But like any bargain hunt it's a hit or miss on what you are looking for & what you want to pay.