BUT, this doesn't mean that I didn't like the Quattro. It's a great machine and one of the deepest that I have ever used, BUT, with that being said: The Quattro is a VEEERRRYYY slow swing machine with a VVVVEEEERRRRYYYY slow target recovery. It really lags bewteen targets, which isn't bad if you only hunt areas where the trash isn't bad like beaches or fields. But for my type of hunting, which is parks, school and an occassioal yard, the Quattro wasn't ideal. It also is a very poor competition hunt unit as well due to the slow or lag between targets. Lastly, the weight of the Quattro wasn't for me because of health issues.
Now, the Xterra 70, is a light weight machine at 2.9 pounds versus like close to 5 pounds on the Quattro. The target recovery is fast, meaning it has a faster target processor then the Quattro so theres virtually no lag time between targets. Plus it's great on the beach just as the Quattro, I used mine during the last comp hunt I entered and it worked great, no intereference from other detectors and I could really whip it around looking for those seeded targets. Now is the deep comparible to the Quattro, so far I would have to say no, but then I've only logged about 10 hours on mine. In my area, In coin mode I think the depth is about 8-9", which is about the same as I get with the CZ5, CZ3d, Cortes & GT&i1500.
I think it comes down to what type of hunting you do and what you expect from the machine, but if it were me and it was, I would and did go with the Xterra 70. But for hunting older sites for deep coins, I wouldn't exclude the Explorer, GT, DFX, CZ3d (it was designed for that) also the ID Edge is another that has a old coins mode, this is just to name a few.
I hope this helps you out, if not email me at mtdoramike@wmconnect.com