I've gone back and forth-first only brands, then tried generics, since costs are rising, some are definate NOWAY! And so back to brands.
Crisco brand-never will switch, tried a generic once, and opened it fresh and it was extremly soft, and it wasn't even warm out.
Duncan Hines-for my mix starter cakes, used to use good ole Betty-since she was cheaper to pick up, lol, but when baking larger cakes(which people want more and more) I found good ole betty wasn't getting done in the center even with heating cores without drying out on the edges.
Powder sugar-c&h, then price nearly doubled, tried generic for MMF-it screwed it up, went back to C&H, then Sm's opened up and had #25 bags of their generic-hesitated, finaly bought and it's fine-except it's raised $4 in the las year
butter-always generic-
nonstick spray-bakers joy, have tried many and that works the best, but sometimes the nozzle get plugged
Marshmallows for fondant found out from trial and err-kraft is the best-but there are a couple stre brands that I don't have issues with (but if they aren't on sale, I'l still buy kraft) and there are some store brands I'd just be throwing my money in the trash-because thats what I'd be doing with the fondant.