I have never used primer on drywall. Quality paint over drywall and mud without any primer. In my own house I re-did the drywalls in 2 of my basement rooms due to water damage and painted right on top of the new drywalls with Behr paint which most professional painter call it crap paint, this was nearly 18 years ago. The paint still looks as good as d
When I started in this business nearly thirty years ago, thirty year painter told me few things, one was: " always prime the walls no matter what, even if the walls look clean" He recommended Ben Moore First Step. (no longer available).
Over the years I would sometimes follow this recommendation, sometimes not.
The best results with the easiest effort always starts with primer.
Primer is less costly than finish paint. So there is a savings there.
Primer allows the paint to spread on the surface better. Makes a labor savings, where you can get away with a single coat.
90% of the times you don't get any surprises on the finish coat.
The end results speak for themselves, no matter what the lighting is.
I find when I prime I never regret it...
Some people love Behr, I've tried it a few times. They sell you less than a gallon. I find it is terrible at leveling.
My personal home, the previous owner painted everything with Glidden and/ or Behr. Some of those colors not only faded but oxidized to a completely different color in some places.
Some one previously mentioned most people develop a system that works. For me Behr isn't part of that system. I won't use it even if my customer provides it. I will have them go purchase off of my account so I don't have to use it. For those people, I find they keep going back purchasing paint for their projects either at BMoore or Sherwin.
Paint costs is far less of a deal in a project as compared to labor. So when you have system that works you're less apt to change it.
