Robert:
I would agree with the previous recommendation to buy any major company's top-of-the-line paint rather than a box store house brand. That's because you only paint the exterior of your house once every 15 to 20 years or so, and so it makes sense to pay more for better paint to make your work last as long as possible.
PS: You don't need to know the rest...
You see, it all revolves around the fact that companies that make paint, don't actually make the ingredients (like the binder resins, pigments and additives) that you find in their paints. They buy them from chemical companies that specialize in makeing those things. For example, most people have never heard of a company called Rohm & Haas, but until 2009, they were the largest manufacturer of the acrylic resins used to make latex paints, acrylic floor finishes, grout and masonary sealers and nail polish for the ladies in North America. In 2009, Rohm & Haas got bought out by Dow Chemical, but is being operated by Dow as a separate company.
So, chemical companies like Rohm & Haas, the S. C. Johnson Wax company and DuPont (with it's TiPure white pigments) are continuously sending their sales representatives around to take the managers of each paint companies out to lunch to explain the benefits of using their latest and greatest binder resin, or defoaming agent or red pigment or whatever. And, of course, each of those newest products comes with a new price, too. Those paint companies are not going to buy those new offerings unless they're convinced that the improvement in performance justifies the incremental cost.
Consequently, when you buy any paint company's top-of-the-line paint, what you're getting is the "best" paint that company can put together at a justifiable cost from all the different ingredients being offered to them.
With house brand paints, things work different. When a hardware store chain like Lowe's or Menard's decides to sell their own house brand paint, they'll do their own studies and surveys to find out what their customer base thinks "good paint" should cost. Then they'll approach several paint companies and ask them for a quote to provide 15,000 gallons per month (say) of paint costing between $17 (for flat) and $23 (for gloss) (say) per gallon so that their stores can sell that paint for $26 to $32 per gallon (say).
Now, since the selling price of the paint has already been established, when the paint companies start working out their quotes, they find out that by buying the resins, additives and pigments in large volumes like these, they can get them at a lower cost, and so they can use better, costlier ingredients and still meet that $17 to $23 cost per gallon specified by the retailer.
So, with house brand paints, because the selling price has already been established in advance, the volume discount the hardware store chain would normally receive in the form of a lower price ends up going to the consumer in the form of better quality resins, additives and pigments. So you can generally get "better" paint for a "good" price when buying a house brand paint.
But, to buy the "best" paint, you need to buy any company's top-of-the-line paint from a paint store.