Hi Terry.
I may be able to throw some limited light here if you like. I own as XS Explorer, which I've got around 30 to 40 hours on, and I bought a GTI1500 earlier this week, of which I now have around 9 hours on. I know that these aren't the exact detectors that you are looking for, or the level of experience, but since you haven't got a bit yet; I thought that I may be able to offer something. From what I've read of the posts here, Golden owns an Explorer as well as a Quattro, so she may be able to tidy up on the minor differences between the Minelab machines.
From what I've experienced to date, the primary difference between these 2 machines, is that you are putting the imaging's help in IDing targets as opposed to using the Minelabs tone system to identify targets. As you have far more experience than I at using the imaging, then you can decide for yourself as to how effective it is. Whether using an Explorer, or Quattro, it takes some time to train your ear to tell targets apart from each other. ie Coins give a flattish even tone as you pass the coil over them. A screw cap will sound similar, but has a bit of a lip on the edges. The metres on the Minelab units are best used as a secondary source of information, as corrosion and coins on an angle, throw the metres out. The GTI's seem to need constant watching, to know what is what. Basically, it's a visual system up against an audio system.
Depth wise, I feel that they are on a par with each other. Some reckon that the Minelabs are deeper, but even my Ace with it's large coil, will out reach the Quattro/Explorer's standard coil. What the Minelab machines will do much better at depth though, is give accurate Visual ID's. The GTI's are limited by having only 2 imaging coils. There are other non imaging coils for them though. The Quattro has a huge coil selection.
Ergonomics wise, the Garrett machine is better balanced but about 6 ounces heavier (180 grams). I find the Armrest on the Minelab machines far more comfortable than the Garrett unit's. The GTI has a back light, the Quattro doesn't, but learning the tones overcomes this. The Quattro's numeric display is a lot easier to see than the Garrett's square icon indicator system. Also the Quattro has a 0 or 40 numeric display.
The only other major difference that I can think of at the moment, is the recovery speed. The Quattros is quite slow. A lot slower than the GTI. This can put some folks off, yet others prefer it that way. It's just a matter of personality. If you want to cover a lot of ground fast, then it's not for you, but if you like to slow down and seek those deep targets, then it's suitable for you. I'll let the folks here go into more detail than I can.
Hopefully this can throw some light on it for you, maybe even provoke a better response. But this is the best info that can give you as my experience level on this subject, is somewhat limited.
Mick Evans.
