Not really. There is a huge difference between what you get at a big box store and what you get at a paint store, even if the brand name is the same.Oh, and that $32 gallon of Valspar at Lowes is Sherwin-Williams paint.
Sherwin Williams might have manufactured it, I don't know, but it is definitely inferior to the high end Sherwin Williams line of Emerald or Duration that you would get at the Sherwin Williams store.
I speak from experience, not from a paid position within the company.
All paint will paint. Some paint will paint better than the other paint. Go with the better choice. It will be easier to apply, it will last longer and it will look better. Plus, why save chump change when the major cost is labor?