Nope...no difference. Check on White's forum...you'll get the definitive answer from the White's techs. The internals are identical. The only thing I see on that pic you posted is it comes with a rechargeable battery pack, which has no effect on performance.
According to the guys on White's website, the DFX is no longer made, but there are still some "new in the box units" at various dealers. Apparently there was quite a run on them when Whites announced they were no longer going to be manufactured.
I think the MXT's have a bit of an edge when it comes to prospecting...they share some of their circuitry with the GMT, which is a terrific gold finder. I've read that in some places the MXT is the detector of choice for prospecting.
When they change model numbers, it's a natural thought to assume there is some sort of upgrade. MANY people have made that mistake about the two DFX models...that's why the question has been asked numerous times on the White's website. Ain't a big deal in any case. The DFX is a great unit. I've really enjoyed using mine, and it solved a heavy trash problem I had at a couple of locales..at one of which it found me my best coin...an 1891 Seated Liberty dime that was dropped in a ranch house at an old ranch that ran in the latter 1800's, and is no longer there. The buildings burned down many years ago, and the site has lots of nails. The DFX "saw" right thru that junk. If I was only going to have one detector, it might be the MXT Pro...but, if I could chose, I'd have what I have...the GMT for prospecting,
I would think the V3i would be dynamite at the 22khz freq....assuming that freq is all that is transmitted. There is some engineering dispute about multi-freq machines and gold prospecting. As I understand the problem, when you transmit multiple freq's into an object, there is only so much signal strength given back...maybe less at one particular freq, compared to when only a single freq is transmitted. With the DFX both freq's are transmitted all the time...you can chose to listen to both, or either, but both are transmitted. That may lessen the sensitivity to smaller targets. Many DFX users say it isn't a good prospecting machine. If my understanding of the V3i is right, you can chose a single freq....and, that's the only one transmitted, which would be an improvement in my opinion over the DFX for prospecting. I think you can also chose, with the V3i, to transmit, and listen to, all 3 freq., which would give a great benefit in trashy areas, for coins and relics...probably better than the DFX., due to the 3rd freq.
