I have been using the AT Pro for a number of years. At the time of purchase there wasn't a lot of all terrain machines out on the market and was pre AT Max.
I got the Pro over the AT Gold as it was supposed to work at the beach which it can on regular sand but NOT around black sand that I soon discovered.
As a coin and relic machine with the stock coil I have found some fantastic finds. People have made Noobtube videos how bad the audio is blah blah and basically don't know how to run even the simplest machines without training wheels of some sorts.
First off separation is descent for majority of places and in high trash areas you may want to consider a smaller coil. Will be ordering a viper for mine tomorrow. Why? I want an incredibly reliable machine for freshwater hunting. AT Pro has never leaked and only problem I ever had was from a winter hunt where I snagged up the coil on a log and cracked it. Garretts top of the line support fixed the machine up for me even past warranty without a hitch and even updated the firmware.
As for depth it is about average but very stable, most places I can run the machine at full gain which keeps it in striking range of majority of finds. 12" silver reale, recently a 10" farthing around iron both with stock coil.
Iron audio is not adjustable but it isn't necessary as the iron audio is vco which meanes when you hear that iron sound it varies by iron size and depth. This is crucial for relic hunting. Iron range is 0-40 which gives you enough numbers to make finite discrimination of the small junk (iron cut nail will break around 33). Compare that to Kruzer and Anfibio machines where iron audio is flat and the same cut nail breaks at 4. Not much wiggle room there.
The machine locks onto targets well making isolating targets fairly easy and especially since the tip or heal of coil are dead on to the target. This makes it easier to run bigger coils and be able to pick out the target of interest with just the nose of the coil.
By today's standards it is a slow machine but so are my Tesoros' but that doesn't make them less effective.
Bottom line solid machine that is incredibly dependable, handles emi well.
Downside, really need a small coil for high trash areas, doesn't handle many salt water conditions where black sand is present. No display backlight. Bit on the high side for pricing compared to what is out there.
As for the AT Max, it is a noisy machine. All metal threshold's lowest setting is too high for me. Nose of coil is good couple inches away from the target. Not that effective at the beach. AT Max is approx 30-50% deeper than the AT Pro but comes with a cost for stability.
If your not doing any salt water hunting then also consider the AT Gold. Has All Metal Mode which can be very handy in hunted out sites but also consider the raider or coil for field hunting.
