Yes, it is true that we can do all manner of creatively interesting things with some of the higher end models from White's, those presently being the XLT & DFX models. But we have limitations just the same.
"The DFX, (as per the printed statement of Mark Rowan, is a Dual Frequency XLT) was conceived as a detector which would maintain most of the popular attributes of the Spectrum XLT, while adding the benefits and capabilities provided by multi-frequency."
I will agree that one of the nice features about the DFX is the quicker 'clock time' so that mode changes occur quickly. Still, the DFX is a moderate to fast motion design, just like the XLT. You can tinker with an adjustment or two or three and make it sort of work like something else, but in the end it is still very similar to the XLT so far as sweep speed is concerned.
The DFX shares search coils with the MXT (and now the Matrix M6) due to the 14.91 kHz operating frequency (the other option is the 2.98 kHz frequency of this dual frequency model). The MXT was designed as a two-filter type, slow-motion discriminator that provides a very quick response. The DFX might have some advantages for an operator due to it's dual frequency design and some of th adjustment functions available, but that doesn't mean it will do the job for everybody.
I have worked with a few different White's Dealers, using their own DFX programs as well as those offered by some White's distributors or dealers of note, and too often the field performance has left them wondering about the merits of selling and/or using a DFX compared with some of the other White's models.
We selected several in-town sites to hunt for older coins, but mainly they were older home sites with yards that were torn up for renovation, or street/sidewalk renovation, or old vacant lots were older homes had been torn down 10-40 years prior and they sort of served as play lots for neighborhood youth.
Through the years I bought three (3) DFX models in order to try and find the right settings to make them serve as "silver shooters" to compete with my friends who clean up on silver coin in the older parks and the like. I was also hoping to find a unit that would serve me well in the torn and dug up renovation work.
What I managed to find was a program set-up for the XLT that came close to the typical settings I use with the 6000 Pro XL, now XL Pro. It doesn't perform exactly the same, but it comes fairly close. I like the XLT but prefer knobs or other routes for quicker adjustments with less scrolling.
The interesting thing I found about the DFX, as have some of those avid detectorist/dealers I've hunted with, is that while the DFX is an improved & modified XLT of sorts, they can't really get performance similar to the XL Pro. Also, they had difficulty trying to match the XLT's adjustment potential.
With the MXT out I got one because I like the knob adjustment, but I still hoped I could tailor the DFX to hunt like the MXT but have the quieter threshold. I was not able to set my second DFX up to operate similar to the MXT. It's just 'different' by design.
I also have been unable, with all three of them, to duplicate the performance I have with the XL Pro, and it definitely can't be tailored to come close to the performance of my modified IDX Pro regardless of the filtering and other adjustments it has.
As for the DC Phase function, I agree. It isn't going to be all that accurate in reporting "how much" of a particular type of ground there is to deal with, but I still feel the MXT's ground reading is superior to the XLT and DFX.
As for autotracking circuitry, there are things I like about it and things I don't, and in this last six months now White's has provided autotracking circuitry in the DFX, XLT, MXT, XL Pro and new Matrix M6, yet no two of them function alike. Still, I have found that by using top quality headphones and listening very closely to most of these models when hunting in trash infested sites, and depending upon the settings, you can actually hear the electronics turning off and on (those with Track Inhibit) or hear slight hesitations during the electronic processing of the ground signal to adjust the GB.
One such littered site I used to develop a like or dislike for autotracking was a fairground where we held a competition hunt back in '98 and '99 and '2000. It was recently plowed and the apparent loose, turned over dirt was appealing to use as the site to plant the various hunt fields for this two-day event. No time to survey the site as we had to get things staked and roped off and planted quickly!
Unfortunately, for some at least, this particular part of the fairgrounds had been used for many years in the past as a dump site of some sort. Mostly iron-based junk but an ample supply of clipped copper tubing and small non-ferrous junk in the mix. It was especially the iron trash, however, that caused the biggest frustrations for the majority of hunters. Many using a Shadow X2, Tesoro Silver Sabre