Promar 200 around here at least is the dog poop of paint. Its whats slathered on condos and rental units by the tanker truck load. It wouldnt surprise me that its no different than home center paint.
Coming from nearly 30 years of residential construction there IS most definitely a difference in paint but there is perspective in there as well. Painting to get the check when you walk out is easy. A paint job that holds and looks good (and I mean looks like the day you walked out with your tools) is a different story. Your contractor maybe either just liked what they liked or the Valspar could likely have been better than the promar 200 and they werent use to painting with better paint.
We once sub'd out some work to a 40 year Union painter who was a super nice guy and touted himself as the end-all-be-all of paint. But he was a union painter, who had to work in restaurants, apartments, and so on... speed painter. We were building reasonably high end residential and running Benjamin Moore Regal, Pearl finish, Aura when it first came out. He couldnt lay on a wall to save his life. We would have to bring in extra material so he could paint a room a second time because the roller marks were everywhere. We could lay on a coat on the same job and walk away and it would look like the hood of a corvette.
It all what they are use to running.
My judgement of a paints quality is not only how it goes on. Its when you walk into a home you built 10 years ago and the paint looks nice, its tight, not dry, caulk work is still tight. Thats the sign of good paint. And someone who didnt roll their roller out dead dry trying to stretch their paint to the end of the earth. A good technique is to measure a couple walls that add up to close to a gallon of coverage and then lay your material on. If you get to the end and youve still got a half gallon of paint in the pail, you didnt put enough paint on.
If your painting a rehab thats gonna get trashed thats one thing. But if your trying to paint once, and make it last. Its gotta be done well.