I had the MXT & got dimes to 6" with wet ground, but we don't have mineral-free soil here. In that same park the Garrett AT Pro got a dime down 7" when soil was totally dry. The AT Pro must be manually ground balanced for best depth & ID. White's has auto ground track. So maybe White's sometimes has an advantage.
I talked to Steve at White's & he said the AT Pro doesn't do real well in their heavier mineralization. For testing new detectors they are developing, White's has 40 soil samples from all over the world.
Any day now, White's will have 2 new detectors, the Treasuremaster ($299 MSRP, $279 MAP price) & Treasurepro ($399 MSRP, $369 MAP price). They will have giant numerical IDs, can be safely used in the rain, use only 2 AA batteries & weigh only 3 lbs. The Treasuremaster comes with 9.5" round concentric coil. The Treasurepro comes with 10" DD coil. The depth reading goes to 10"+. They will have auto-tracking (the Treasurepro includes lock option for trashy sites), threshold to help hear the weakest beeps. They also have a beach mode. There is a little triangle in a circle that points to probable target.
There is always new software & other new ideas by design engineers to make detectors better &/or cheaper, and the reduced weight should enable many to detect more comfortably over many hours. The large numerical IDs will help those with bad vision to keep using the visual IDs. I'm thinking these detectors are likely replacements for the Coinmaster Pro & Coinmaster GT, as the prices are the same despite improvements. They can use any coils for current Coinmasters & recent Prizms, as the operating frequencies are close. I hope the IDs will be less jumpy. Will be watching for 1st reviews. Best wishes, George (MN)