Two totally different machines. The Explorer is an FBS unit like the Etrac and CTX. The Sovereign and it's waterproof version (The Excalibur) are BBS machines. BBS operates on 1.5 to 25khz. FBS on 1.5 to 100khz. For those two reasons there are certain beaches or mineralized soil sites where one will handle the situation a bit better than the other on targets. For instance, an old rule of thumb in some grounds is lower frequencies penetrate mineralization better and run smoother. For me in my soil/sand that's been true for me over the years owning a lot of machines out there.
Since you said you are mostly a audio hunter the audio between them is very different. The FBS units have a more short report, while the BBS units have long drawn out audio with a lot of fine details since it's not sent through tons of processing. Just the same, the Explorer is known among FBS units as to have some distinct audio traits on silver not really seen as much on the other FBS models. I can tell you the audio on the Sovereign is like the best of the cream of the crop old analog machines- long, detailed, drawn out, with a lot of "meat" to the signal to let your ears pick over, yet it also has the numerous tone alerts of a Minelab. The Sovereign is a digital machine, it's just that the audio is more "analog" in many ways. More "close" to the source so less IMO is lost in translation.
Using a meter for depth? Then you are looking at the Explorer because it has an excellent vdi screen with a depth indicator.Me? I always went by sound to judge depth more than a meter, so so long as I have good modulated audio to judge the target depth by it's volume I'm not one to need a depth meter. Depth meters are no more accurate then judging the target's depth by audio IMO. Owned many machines featuring both methods and it's pretty much a wash to me. But if you like to see a # for that your choice is clear- Explorer.
The VDI meter on the Sovereign doesn't tell you depth, just the conductivity # of the target. The bonus though is that it's got extremely high resolution in the foil up to copper penny range. A useful tool for nickels or say splitting hairs on junk to try for gold rings. Highest conductivity span of any machine on the market I've owned or am aware of. If you like to ID coin types though then it's once again Explorer all the way.
Everything above copper penny on the GT is lumped into the 180. For me, when old coin hunting, if it's super deep or shallow but mixed in trash, I don't care what kind of coin I think it is because I'm digging it. I've dug too many silvers over the years that high VDI coin resolution on various machines has told me it was one coin when it turned out to be another. The conductivity difference between coins is very slight above copper penny. Being worn, mineralization, depth, orientation in the ground, masking, etc...All these things can make one coin look like another. Only thing I care about IDing when old coin hunting is zincs when they abound by the millions, and the GT will ID those as a lower #. Terms of nickels, you can ID them distinctly from tabs on the GT due to it's super high conductivity resolution in the foil to copper penny range. Nickels are usually around 143 to 146. Tabs start at about 149 or 149 and go up to 169 99.9% of the time.
Far as iron goes, all the Minelabs will do well in it provided you sweep slow. I can tell you the Iron Mask ON feature of the Sovereign has pulled me coins out of iron like I've never seen on a detector. It was hard getting used to iron nulling out on it though, because I was always one to listen to all signals so I can map out a site in my head. Just the same, now the nulling on iron has kind of grown on me. More peace of mind when I'm trying to listen for the faint hits and such. The stock 10" tornado will separate left/right wise very well. In fact, scan down the page to a video I posted about a week ago where I'm testing 4 different coils. You tell me how left/right separation can get any better on a machine? The Minelabs may be slow but recovery speed is a non-issue with a good quality DD coil with a sharp DD line. But back to Iron Mask...When two targets are at the same depth and overlapping and thus washed in the field at the same time, that's when Iron Mask on the Sovereign does it's magic. It'll ignore the iron yet try it's hardest to pull any non-ferrous (like coins) signals out of the mixed signal. It's a wonder to behold sometimes how well of a job it does at that.
A few more perks to the GT- Ability to easily chest or hip mount the control box for a lighter shaft and easier access to the controls, or for water hunting. All the coils (even aftermarket ones) have extra long cables for that reason on the Sovereign. Meter can be thrown on or off for wading and such too. The analog style controls are also unique. Far as the meter goes, it's not highly processed so the VDI # report is instant. What you see you instantly see the VDI # on, so no lag between that and the audio which can happen on machines with a lot of processing going on of the audio and VDI. One can say one thing while the other is lagging behind saying another.
Far as other perks to the Explorer, I've owned 3 and #4 (An SE with a 12x10 on it) will be coming back into my line up sooner or later here. The screen on the Explorer is mesmerizing and fantastic in many ways. I prefer the VDI scaling on it over the Etrac/CTX because the way it's arranged the smartfind cross hairs seem to give me more clues as to what the target might hint to be. I know many disagree but I'm not a fan of the 12th line compression thing on the Etrac myself like some others aren't either. If you read Bryce's reports in the Explorer forum the Explorer is just a different FBS machine, not something less, and he owns them all yet the SE is what he mainly uses it seems.
So there is a basic outline. The Explorers and the Sovereigns might be by the same company, but they are like night and day in unique traits compared to each other. Nobody can tell you which you'd like best, or which will do best in your unique soils or sands, so I'd tell you to try to locate some local hunters and use both for a while to see which meshes with your personality best. Having that best "match" and understanding with a detector is where things are trully pushed byond a machine's ability on paper. Whichever machine does that for you is the one that you'll do the best with. For me, some days I want digital and some days I want "analog", so I'm keeping both in my line up.
One of the main reasons I got rid of my Explorers over the years was at the time it was pretty much just the stock 10" coil as the only real option (unless you got a WOT), and I was NOT a fan of the 10" Explorer coils. Now that the 12x10 and other options are out there that main issue is resolved for me, hence I'll get #4. The stock 10" coil on the GT or Elite is not the same coil. Much better coil than the 10" Explorer coils IMO. I believe the 10" FBS coils were the main issue with chatter and other performance factors I was having issues with in my soil. I've seen what the 12x10 can do for a machine in terms of depth, separation, and stability on my GT, so that's why I'm strapping one on the Explorer for round 4.
Either machine is a great option for anybody, but they are night and day in terms of unique qualities and traits compared to each other. For that reason you need to try them both and decide from there which matches your personality and style of hunting better. If everybody was the same they'd only made 1 car, although it looks like Minelab is greatly reducing the variety of what cars they have sitting on their lot for sale now.
