I have just returned from central Colorado, near Alma. This is my third season in Colorado with the V3/V3i. In our group we have had MXT's, GMT's, V3's, V3i's and a couple of Gold Bugs. The guys with the green machines were invited, but they didn't show up.
The V3/V3i's have not taken a back seat to any of the detectors listed! The ground is severe. The v3i will ground as good as any detector out there. In this environment, 3 or 4 pumps will not cut it! There have been many posts about how to ground balance a Spectra and some have said 15 or 20 pumps. That is absolutely correct and sometimes, more pumping may be required, but the V's will handle the bad ground---period! The procedure only takes a few seconds and your ready to hunt.
I do recommend a smaller coil and slower sweep. Have used the 10" DD and the 4x6 shooter and both work well, but the shooter is my choice up there. There is a lot of mineral noise, popping and whanging. The smaller coil makes it a bit easier to interpret what you hear.
As I said earlier, no detector beat the Spectra's. I cannot say that the V's shamed the other detectors, because we all did pretty well. We were not actually comparing signal to signal, but I did follow one fellow up a hill and found some targets that he missed. He was using a GMT and I think experience was the difference there.
Personally, I think if $$$ are a concern, then the MXT is a good choice, but if you can afford one the V3i is the way to go.
One hell of a metal detector.