Depends on the store. Trader Joe’s ketchup is good, but not the other major chains. For mustard, it’s worth finding the local German store or butcher and getting real mustard.
It used to be there was no store brand ketchup, but there was McDonald’s ketchup. I always buy Heinz, which has sugar.
Mustard is dijon or brown, and those are both store brand. I also like buy Bavarian sweet mustard which is called Händlmaier’s Süsser Hausmachersenf.
Trader Joe’s Whole-Grain Mustard is excellent. I’ll have to try the Garlic Mustard Aioli.
Surprisingly, Ikea whole-grain mustard is very good (I’d rate TJ’s higher, to my tastes, but both are good). Ikea regular mustard is also really good; not as pungent as regular yellow mustard, and very mellow with a slight cardamom taste. I’ll eat it bt the spoonful.
As far as regular supermarket brands, I only ever really loved Inglehoffer whole-grain mustard, but TJ’s is very close, and a huge bargain.
I go with brand names more often than not. For ketchup, I go with Heinz most of the time. For mustard, I usually have more than one type in the house. Yellow is generally French’s but I’ll sometimes buy a regional or store brand. The same is true with dijon (Grey Poupon), stone-ground (Gulden’s), and my favorite kind, sweet-hot, which is usually Beaver Brand.
As a Pittsburgh ex-pat, I used Heinz ketchup most of my life, and plenty of it. The past few years, i switched to Hunts, as it’s considerably cheaper. Looking online, my local Walmart sells Heinz 20oz for $2.23, and Hunts 20oz for $1.19. Now, I prefer Hunts. I became used to it, and in the end, one is not superior than the other: they’re just a little different.
I don’t buy store brand. I found it watered down, both in taste and thickness. It’s $.88 for 24oz. Guess I would get used to it eventually, but Hunts isn’t that much more expensive, not like Heinz.
It’s always Heinz ketchup here because that’s what my wife and kids wanted, I only use it as an ingredient. Mustard matters to me, I don’t like the standard yellow mustards, they taste more of vinegar than mustard to me. There are a lot of different mustards I do like but my go-to based on availability is French’s Spicy Brown mustard. When I was a kid I liked Mr. Mustard a lot, which seemed very spicy to me back then, but it’s been so long since I had it I don’t know how it would compare now.
I buy Heinz ketchup. It’s what I like, and it’s not expensive. For me, cost is an important consideration for expensive things like refrigerators, not cheap things like ketchup. I’ve considered buying fancy ketchup (like Sir Kensington) just to see what it’s like.
I don’t like yellow mustard for most things. I use Bertman’s Ballpark Mustard instead. I buy it mail order, so it’s relatively expensive, but I’m not going to go broke buying mustard.
I’ve got Best Foods / Hellman’s mayo for “bulk” uses like egg salad, and for my partner who doesn’t like Kewpie.
There are two different kinds of Kewpie. The American-made version comes in an ordinary bottle and has no MSG, but the imported stuff in the floppy squeeze bottle in a plastic bag does have MSG. Some Target and Walmart stores carry it, and I’ve also done Walmart’s ship-to-store option. The cost should be about six bucks - there are sellers on Amazon and Walmart’s “marketplace” that are more than happy to price-gouge at twice the price.
For Ketchup, I get “Simply” Heinz. It’s not organic, but it’s got less odd stuff that does’t need to be in ketchup.
In mustards, I go with either French’s yellow or Gulden’s spicy brown. Once in a while I’ll let my hair down and buy something weird like chinese hot mustard or a honey mustard.
As mentioned above (by me), it has yeast extract, which contains concentrations of glutamic acid, as MSG does. I’m not here for an argument about MSG vs other natural substitutes, but if someone is sensitive to glutamates, it’s worthwhile to point out that it still does contain plenty of glutamates so they are informed enough to make their own decision whether to eat it or not.
Boetje’s is made locally, and I love it.
I don’t eat ketchup, but I do buy it occasionally for the food pantry, and for this, I do get brand names.
I buy Heinz ketchup. It’s one of those items that’s pretty much always on sale, and the sale price is roughly the regular price of all the other brands, so I keep buying the Heinz.
Prepared mustard, I have no preferences. I buy whichever spicy brown mustard is good looking to me at the moment.
Dry mustard, the only brand I’ve ever seen is Colman’s, and a tin of that will last me for years.
My ketchup choice is pretty much what’s the cheapest when I go to buy some. I rarely use it for dipping, sometimes use it on burgers and I don’t make those much, and mostly use it for meatloaf glaze and salad dressing color.
Sorry, submitted too soon. Continuing…
I don’t prefer chunky mustards. My normal mustard is Aldi Burman’s Dijon or it’s local equivalent, there are a lot of private labels of the same stuff. They’re really good! I don’t normally keep yellow mustard around and primarily use it for sticking rub on meat before smoking.
Yes, ketchups taste different. I like Heinz, although I don’t eat a lot of ketchup. Frankly, given how much ketchup we eat, the cost is totally insignificant. We keep it in the fridge so it doesn’t mold…
There are lots of kinds of mustard and the all taste different. I don’t care for plain yellow mustard, although I like some of the chunky ones in moderation. We use more mustard powder and mustard seeds (both of which are delicious) than prepared mustard.
Ketchup, mustard, peanut butter, milk, salad dressing, white bread, gasoline, etc… They’re all pretty similar to me and I don’t give a hill of beans who made them. I just buy what is cheapest.
Until a couple of years ago I didn’t even know that French’s made ketchup. But after Heinz closed a plant and fucked over a town and a bunch of farmers French’s stepped in and bought the plant and started buying tomatoes from the local farmers. I’ve been buying French’s ketchup since then. I have always bought their yellow mustard as well, but I do buy other mustards too.
I don’t know why but I can never find a reliable source for “Spicy Ketchup” at any of my local stores. Store brands will pop up then suddenly be gone for months then pop up again, and nobody seems to stock the “big brand” ketchups spicy versions.
You can go online for the good stuff my heat-loving brother says. I suggest dropping some sriracha in it because sriracha is also sweet so it should blend well.
If you can’t discern much difference between peanut butter and gasoline, we’re assigning the cooking chores to someone else 
I buy the cheapest, mustard and ketchup is pretty basic no matter who makes it.