and some comments
AT Pro vs. Max
The biggest change to me is the audio swap. It takes the audio signals from the AT Gold and puts it in the AT Max. So the sounds/signals you have memorized from the AT Pro do NOT apply anymore. It's completely different. That's a massive shock to the system. The quarters/silver sounds way better on the AT Pro. But as you get used to it, you'll learn the new signals. If you are an AT Gold user, it won't bug you at all.
Way more items found. Better depth. The AT MAX does much better in comparisons of finding depth targets. It's find all sorts of targets my AT Pro missed in heavy trash area parks. I've gone over an area 20+ times and this thing dug another $10 worth of change out of the same area. It also gets you digging more nickel 50-70 range targets which are likely to be gold because they sound more meatier.
=Z-Link wireless headphones. That before was alone a $125+ upgrade with the headphones. For 5 years I've been tripping on my annoying headphone cord. The headphones are rechargeable too.
=back-light. I've been using a headlamp that I shine on my unit. This version is way better. It does eat up more battery though. I do almost all my digging at night and this thing is doing great at night. I love the new display.
=Volume control built in. Before you have to use your headphones which is hit and miss. This feature delayed the release of the unit for months but most agree it was worth waiting for.
=Better ground balance. This makes this unit better than the Garrett AT Pro in mineralized locations and the BEACH. I don't know about you but my AT Pro sucked at the beach. I never found anything except in the dry sand. That's a huge reason to upgrade. Supposedly it's better at the beach but we'll see.
=Adjust the background noise +/-. That's new.
=Free Hat, awesome! It's kind of a generic "free" hat but who cares. I've been wearing it since I opened the box.
=LARGER VDI numbers. Much better. It's hard to see the numbers on the AT PRO sometimes.
=Better rubberized hand grip instead of the foam or whatever it is other one from AT Pro/Gold.