Well, the GTP 1350 is new, so it automatically gets lots of coverage on the forum, as people have lots of questions, and I have posted most of my hunts with it. They are different...well sort of. The GTP 1350 is a watered down version of the GTI 1500. It only has 3 sizes whereas the GTI 1500 has 5 different sizes. Also, the way the electronics calculate the sizing are way different too. From my experience, both different types of sizing work equally well. The GTI 2500 still gets lots of coverage, because it is the top of the line machine Garrett produces for land hunting, and therefore has more options. There is a longer learning curve with the GTI 2500, so people who get one tend to hang around the forums longer asking questions. It's a great machine once tamed. The GTI 1500 has been around for a long time.....lots of people own one. Ever notice why there are so few posted for sale??? Because they are a great machine and every one hangs on to them.
Hope this helps Rudy......