I used to have a two-monitor setup with a Dell (? not sure) and an Eizo, both using the exact same panel. I started with one monitor and then got the Eizo. The difference in picture quality and eye comfort was absolutely jaw-dropping. Dell looked and felt like a complete junk in comparison.

Make what you will of this, but it's not just a panel per se, it's also how it's integrated and used in the whole product.

There are a small handful of panel manufacturers, that's true.

Companies like Eizo typically have agreements where they will take the cream-of-the-crop panels though.