Think of the Excalibur and the Sovereign as different tools.
If you dive, or shallow water hunt above waist deep you will need to use the Excalibur as it is water proof to depths of 200 feet.
If you live in an area where it rains constantly, an Excalibur or any water proof detector is ideal as you don't have to worry about moisture damaging it as it is water proof.
The price that you pay for this ruggedness is that the detector is heavier, costs more to buy and maintain as it has to be built stronger and pressure tested. You also loose flexibility as the head phones and coils are hard wired and cannot be changed to meet beach conditions. Also, as it uses an older Sovereign technology it is less capable than the current Sovereign GT.
Yes, you can be more flexible by installing water proof connectors so that you can change headphones and coil size. But that becomes a weak spot and voids your Minelab warranty.
Now let's look at the Sovereign:
As long as you keep it dry and protect it from moisture it is the detector of choice.
You can rapidly configure to the beach you will be hunting on.
For instance, you can change to a 15" WOT coil to detect deeper targets and cover more area rapidly. You can also use the SEF coils which detect deeper and are easier to pinpoint than the standard DD coil. You can sweep the large coils in the water, but there is is more drag
Switch to an 8" coil for detecting in trashy areas such as beach entrances, parking areas.
You can also use it to detect up to knee deep in the trough. You could, but I wouldn't because if you slip and it drops into salt water, the detector is toast and you are the owner of an expensive door stop. Most treasure hunters use the standard Tornado 10 inch coil Double D coil as their go to beach one.
You can also hear the tones better as there do not have to holes to equalize water pressure. You can change head phones for different wind conditions plus get head phones that have limiters to protect your hearing if you go over shallow coins while searching for faint signals.
You can easily break the Sovereign apart of ease of carrying and rapidly change from shaft mount to chest mount of hip mount.
Before Minelab stopped production of the Sovereign, it was heavily supported by other manufacturers . For instance you could buy a VI meter from Minelab or Sunray which would be ideal for coin shooting in parks.
Or you could buy and install an Sunray S1 inline probe for ease of finding targets in the hole, the 1" tip of the probe would work like a minature search coil in narrow areas such as cracks in a reef or between rocks.
Of all the knobs, the notch filter would least likely be used by beach hunters, as it could notch out the return signal from gold which varies over a wide range as it is alloyed with other materials, E.G. (copper, silver, zinc, silicon, nickle) for hardness and color.
Normally, you would not set your discriminator above 3, I use a lower setting of 1 as I want to hear all tones so that I know what is under the coil. With practice you can identify most tones except can slaw. As a rule of thumb, you dig when you get a repeatable tone as beach sand is soft.
Like the Excalibur the threshold on the Sovereign nulls when you go over ferrous metals (iron) and the pitch changes to the next metal object the coil goes over, which takes a little getting used to.