Sandman, how do you know the OP is planning to use the machine on the beach? I will agree that the AT pro is not my first (or even second) choice for beach hunting in the wet sand....but it does a very good job everywhere else I have used it. Also, of the great beach (wet sand) machines that I have used(mostly multi freq Minelabs) they did not do great when put in areas where nails and other iron were abundant. Most of these machines like the Sovereigns, Explorers, CZ's are just to slow at recovering and will miss what a faster machine like the AT machines will see between the nails. I am just saying that there is a tool for every job....and a better tool for every job.
As to the original question....I have not used a AT Max yet, but from what I have seen so far, I will be considering upgrading my Garretts to this machine. It has everything that the previous machines from Garrett have lacked and looks to be just what I would have added. Also, the new detector is suppose to be "better" on wet sand than the AT pro. And the AT pro will do ok for the average joe that visits the beach 1 or 2 times a year and is ONLY really trumped there by, like stated above, a multi-freq detector.