hmm I'd personally vote for Oasts and Coasts as you get to see all of Kent, plus there's a control in an ice cream shop and I stopped for half a dozen oysters last year before riding the last 100k.
Cruelly stripped of its AAA points this year for some reason.
The best Kent audax is Man of Kent 200 calendar route.
Flat audaxes are boring, I learnt it the hard way.