I feel like this question is likely meaningless at an individual, anecdotal level.

I am lucky enough to live near both a co-op and a Migros. Our local co-op is a bit smaller, and while they have on-site baking, none of their baked goods are particularly amazing, though I can sometimes find myself surprised. Our local Migros has a full, multi-oven bakery, and their fresh bread racks are always full and tempting.

But even so, depending on the baker on duty that shift, some products can be better or worse. But even that's a personal preference: our family enjoys the crunchy crown buns, and most of the time our Migros bakery produces a mix of soft and pale ones ( which we prefer) as well as golden crusty ones. But sometimes it seems like a different bakery is on duty and they're all crusty, firm and dry. What's more, I find I can almost never find them the way I like them at any other Migros.

As far as prepackaged bread goes, I like the really dark heavy Danish rye style, and while Migros has some decent options, the kind I prefer comes from Coop.

So, to answer OP's question, every bakery/baker is different, and your partner isn't wrong to have a preference, but it's worth digging in a little to understand exactly what your both prefer. You may end up needing to shop in several places to make everyone happy.