The G852 is the Exedra, first introduced around 1984. The Exedra Max is the updated version and is claimed to be a far superior tyre to the Exedra because of improved compound which gives longer life and better grip. I've only used Exedra Max on the rear so I can't comment on whether it's actually better, although I did try an Exedra on the front and was very unimpressed with mileage (grip was good though).
The Max on the rear gives me double the mileage I got out of Metz and 50% more than Avon, grips much better than both, especially in the wet, and I really like the advantages of the higher profile - better ride, taller gearing, improved clearance, looks etc. Simply better all round.
I'd go with the Exdra Max over the Exedra (G852).