How I painted the interior of my well known Argosy "contemporization" is detailed here in post #181:
I used Benjamin Moore OIL based paints and, several years later, the walls are still in perfect condition.
However, after many years of using BM I recently used Behr on a project. It is every bit as good as Moore for half the price.
Consumer's Report rates it higher too.
I've come to the conclusion that you pay a premium for Benjamin Moore that goes to subsidize all the hype and advertising. Somebody has to pay for that: it's us.