I can only speak about what I have owned and used.
I had a Beach Hunter ID, good machine, but IMO the battery door is a poor design and you have to be very careful when changing batteries. You could not dive very deep with BHID, and watch the battery door, mine leaked twice and was repaired by Whites under warranty, I traded it in on a new Sovereign GT.
I loved my Minelab Excal, and the way it scored at the salt water beaches, but it is heavy for land hunting. Once I tried the Sovereign GT, seeing what a fantastic machine it truly is, it became my primary dry/wet sand, shallow water detector and the Excal became strictly my surf detector. I got lucky and found another Sov GT for sale that had been customized and was water proofed, I bought it and the Sovereign GT has become my primary water detector, the Excal is now my backup water machine.
Minelabs null on iron and are not affected by blacksands, and are highly praised by their owners.....When they say it "nulls on iron", you still know when the iron is there as you recognized the null as meaning "it's iron"....the good point is they will still tell you when there is a gold ring right next to an iron nail.
Water proofed Sovs are rare, and hard to dive with, but with the Excal II out now, you can pick up a good used Excal 1000 or 800 for $500-$750 used. You want be disappointed if you decided to try the Excal.
Good luck and good hunting.................