The GTI 1500 can use the 5x10 scorcher DD coil, the GTP and Ace can not.
That alone is the reason i have a GTI 1500. Over bad soil this 5x10 DD is a must have coil for better depth, target ID and separation. If a coil like that would be available for the Ace 250 i would buy one in a second. With a coil like that the Ace would beat high priced detectors in mineralised soil on depth.
The GTI 1500 and GTP 1350 have the same performance and ground tracking.
The GTI can size ONLY with the imaging coils, but has true depth and size. The GTP can size with ANY coil but doesn't have true depth and size. That means the GTP will see a deep coke can as a small target and the GTI will see it as a deep large target.
The sizing or better profiling on the GTP is not really necessary, because the GTAx1250 could already size by the long, medium or short tone.
The Ace has some advantages over the GTI and GTP detectors....yes, hard to believe. The Ace is very lightweight uses only 4AA batteries and has a faster recovery speed than the more expensive Garretts. If Garrett would make a 5x10 DD coil for the Ace i would sell the GTI 1500.
If Garrett would make an Ace based detector with a true all metal mode of the GTI 2500 and ground tracking and a 5x10 DD available for it, it would kill there own GTI sales.
Andy,NM