Not sure I can convince you that the Deus is a must have, but I would say some of the things that sets the Deus apart from the detectors you mentioned (beside the obvious features you already mentioned - light weight and wireless) are:
The Deus can be programmed to operate at 4 discrete frequencies, 4, 8, 12, and 18 khz. Not just frequency shifted. Of course it is not a multifrequency detector like the higher end Minelabs (E-Trac/CTX 3030 or some of the Whites), but switching frequency on the fly is an effective secondary "discrimination" method to ID rusted bottlecaps and other Iron junk that might ring up high. That is, the Target ID (TID) number will change with a bottlecap opposite of a keeper target if you switch frequency. The multiple frequency options also help increase the chances of cutting out EMI that may be prevalent on one or more of the base frequencies. Plus there is a visual TDI mode (X-Y graph) that can be used to visually identify probable junk targets.
You can almost infinitely program the parameters to custom hunting profiles and you can hunt in Disc mode or All Metal VCO mode (Gold Field) and the full tones discrimination mode (Disc can also be set to 0 if desired and multiple notches can be set if desired) really paints an audible picture of the target vs. set ring tones, because distortions in the e field around the target such as what might occur with an irregularly shaped junk target vs. a coin can be heard on the trailing edges of the tone as the coil is passed over the target. You could even program the tones to sound almost exactly like an AT Pro if that's what you want. Multiple ground balance modes including fixed, tracking, pumped, and wet (salt) sand bias can be used.
The responsiveness (recovery or reactivity in XP vernacular) of the detector can be adjusted across a range well beyond any detector out there today, which really helps in trashy areas.
i think these features are great and balance out the most significant "weakness" of the XP design (and in a true double-edged sword analogy, may also be its greatest strength), namely, that since the coil contains most of the brains of the detector and is actively powered by its own battery, switching coils is not an inexpensive proposition. You are basically buying a new detector when you get a new coil. Here's the upside to that downside, if you have both the wireless headset and the wireless control box (the typical setup) you can pair each coil to both or one coil can be paired to the headset and one coil can be paired to the control box (which has a jack for a traditional wired headset) and voila, you have two detectors (the controller on the wireless backphones can also be detached from the backphones and either paired with a third party over the ear set of phones, used standalone on your wrist or mounted to the coil stem handle, or connected to an inexpensive headphone adapter to provide a wired headphone setup if desired. Finally, if your head is not already spinning with the wizardry of all those wireless options and the multiple configuration permutations they enable, XP is planning on releasing a wireless waterproof pinpointer that can be paired and used in conjunction with the Deus integrated with the coil to allow automatic switching between the coil and pinpointer when the is switched on. I don't find the lack of specialty coil options to be a drawback because, for me, the 9" coil can be electronically programmed to work like a sniper coil in high trash or a deep search coil in relic hunting situations.
All software upgrades are free downloads and can be uploaded to the control box using a usb cable.
Finally, it is very easy and cheap to weatherproof and shallow water hunt by simply purchasing a waterproof phone case for the cell phone sized control box for less than 10 bucks. And there are ways to make it a surf machine with a little more investment in $$. Though personally, I would use a dedicated surf machine if I was doing extensive surf hunting/diving.
I am sure I missed something since this was sort of a stream of consciousness write-up but hope this helps.
