Here is a note I sent to a friend who's contemplating a Deus also (this doesn't cover all perspectives/detector uses and is just my two cents on some features--some may disagree...):
With regard to the Deus, the first thing to remember is don't believe any prices you see advertised. Contact a dealer; they'll give you their best price which is lower than you see advertised. Try xxxxxxxxx if you don't already have a dealer. You'll probably want what they call the WS-4 or the WS-5 package with either the 9 or 11 inch coil. So there's really just two choices to make: what kind of headphones do you want and what size coil do you want. You don't want the Starter package which is cheaper, but does not come with the remote, which is an invaluable tool in my opinion. Even the hardcore Brits use the remote

Going without a remote means you dig solely by tones...no visual TID, VDI, depth meter, etc.
So, the WS packages include EITHER the full WS-5 headphones which look similar to stock headphones from most companies--they're better than most stock phones and are designed to cup the ear to cut out external noise, which they do a decent job of, but not as well as some aftermarket phones like Grey Ghost, which I use. OR the WS-4 headphones that are very similar to the free headphones you get on a plane trip, but they're backphones, meaning the headband lays behind your head. They don't cut external noise as well, but are good in hot weather...they tend to be on the flimsy side too. One thing you can do when you order (if you don't want to use the WS-5s, is tell your dealer that you want the the Grey Ghost headphones instead of the WS-5s--XP carries these headphones as an alternate option to the WS-5 (you'd receive the WS-4 headset and the Gray Ghosts--this can be confusing, so let me know if I need to say more). I had the WS-5s for a short time, but had XP replace them with the Grey Ghosts because they're sturdier and cut out more external noise. There are a couple of other aftermarket headphones out there, but XP doesn't carry those....some Deus dealers do though and we can talk about this more later if you're interested. This whole discussion is probably very confusing, but once you look into it, it's very easy...and we can talk more extensively when you're ready to buy.
So after choosing your preference of headphones, the only other decision is the coil size...right now there are three sizes to choose from and they're all DD coils. There's the 9, 11 and 11X13 coils (the 11X13 appears as an accessory I believe and does not come with any of the offered packages--I don't know if a dealer could make a deal with you, but if you're interested I'm sure they'll discuss it with you). The 11 and the 11X13 have similar capabilities. The 11X13 is only slightly heavier but I've read where it isn't balanced as well as the 11" so it does seems even heavier. From all the reports I've read, those who've used both tend to agree that it's worth giving up the very minuscule depth capability difference for the better target separation and lighter feel of the 11 inch coil. Assuming you've ruled out the 11X13, we're left with the 9 and 11 inch coils. Traditional thinking with regard to coil size would have you considering your hunt sites, whether they're trashy, contain iron or contain deep targets. That all comes into play of course, but with the Deus, there are two more considerations. The 9 inch coil goes deep--very deep. Of course, the 11 inch does too...deeper in fact. So, like in the past, you may consider getting a larger coil for deeper targets that you may hit just fine with the 9 inch Deus coil. I'm not saying the 9 inch on the Deus will match the depth of the stock coil on the eTrac, but I've heard it's close. It doesn't cost you any more to get the 11 inch coil instead of the 9 inch coil, so if depth is your motivation, then the 11 inch is what you want. Now, the other consideration is target separation. I used the DFX in the past and I've stood side-by-side with my Minelab Explorer-wielding buddy...neither machine can touch the target separation of the 9 or 11 inch coil...I truly can't explain to you how such a large coil (relatively speaking) can separate like a 5 inch coil--it's truly impressive. I started with the 9 inch coil when I got my Deus and bought the 11 inch later because I wanted to have maximum depth and target separation for some of the places I hunt. Having used both coils, I can honestly say that I can barely tell a difference in the separation capability between the two coils....barely. It's almost indiscernible, but I do notice an ever-so-slight performance improvement in trashy sites with the 9 over the 11 inch coil. Part of the reason may be due to the fact that the 11 inch coil simply "sees more" when it's over trash or iron.
For my style of hunting and the sites I hunt, if I had to choose one over the other, I'd choose the 9 inch coil...but I'm glad I don't have to choose because the 11 inch coil gives me that slight depth edge when I'm on sites where I feel targets are deeper and it covers ground quicker. There's a ton of opinions about this in the forums, and I think it comes down to your site preferences...contrary to my perspective, many, many people feel they only need the 11 inch coil, which is probably right for their situation. One thing is for sure, regardless of whether I'm using the 9 or 11, I cover ground much faster with the Deus than I have with any other detector. I don't have to spend as much time separating targets and I get the same results sweeping faster.