Here are some questions (as I understand them) to ponder regarding primers:
Will the there be a top coat?
Will the top coat lift the primer?
What primers are proven effective with all the RV aluminum alloys?
Does my selected primer pass the salt spray, and weather exposure testing?
How do I want to apply the primer?
Is my selected primer available for the method I want?
Is only one primer required for the whole plane?
Answer these questions and you can select a good primer.
Now - as a community - what corrosion problems have been seen in the RV fleet? Cessna? If there are no issues, then, is a primer needed? Can an inappropriate primer accelerate filiform corrosion?
The answers are a lot longer than the questions, thus primer wars. All is within VAF.