Simple choice in my view …
Tough or Pretty?
If I want already surface rusted parts rust proofed and long lasting then the best I’ve used is Por15 rust proofing paint with their top coat on top. A bit of graft to do properly but done once to last.
Powder Coat is very good with better finish.
Why not try and test in severe salty weather both options on some small parts then choose.
Your call.
Roy