My experience (hey, somebody's
got to evaluate the if-it-takes-more-than-2-minutes-to-prepare-forget-it) products:
Products involving fats (any kind) or sweeteners (almost any kinds) are where the brand-v-generic comes home to roost.
Canned nuts - Planter's are the only ones I'll buy. The house brands are too dry - and the Walgreen's brand should not be mentioned in polite society.
Ice Cream - I don't need the "super-premium" ones, but one (either Albertson's or Safeway, don't remember) has a super-economy product that tasted as if it had more artificial emulsifiers than butterfat - the first time I ever threw out ice cream.
I once decided that the outrageous price of Smucker's ice cream toppings could not possibly be justified, so I tried Smart and Final's pineapple topping. That was a mistake I'll make exactly once, but I still suspect the Smucker's price is outrageous.
Interestingly (or not), the triviality of stick pretzels is another - being from the midwest, I used Nabisco, which are rare in SF - even the SF natives asked where I got them - they are/were that much better.
And the less said about "Farmer John" breakfast meats, the better.
Booze is another - rotgut is fine for mixed drinks, but, if I'm drinking it neat (straight), I'm going to go for the high-priced spread.
Since american beers are generally dreadful, splitting hairs seems futile
And one I would have preferred to not have had the opportunity to learn:
My car was stolen and recovered. The thief had actually gotten fairly well moved in - clothes, groceries, such stuff. Among the groceries I got out of the deal were 2 cans of orange juice and a few cans of beans in tomato sauce. These are marked "not for sale - for use by community or tribal food assistance programs". I haven't tried the beans, but the OJ is about as bad as I can imagine it could be and still be approved for human consumption - even the cheapest fresh oranges are sweeter than this stuff.
Do we need to mention Banquet brand frozen dinners?
so yes, go for the cheapest stuff that works, but pay attention when it comes to items using expensive additives - sweeteners, oils, booze.