Less pulltabs, foil and junk in the wet sand.
I have the Safari but have never used a Sovereign. I believe the Sovereign is essentially the same as the excallibur but not waterproof. If that is the case then from what I have seen all three are very good for beach use. However I would bet the Safari will out perform the both the Excal and the Sovereign in wet or dry beach sand. Maybe because it is FBS or maybe because of its 11" coil but really, how deep do you want to dig?
This is me pulling a bullet shell out of slightly wet sand about 18" down
http://www.youtube.com/watch?v=NI63NiTcOzg
^ advance to the 4 minute segment
Maybe if I didn't waste my time here with this I would have found a diamond ring shortly after instead? Hey but I'm new.
First thing you will notice going from an ACE250 to any of these Minelabs is going to be the weight. You might not like it, better try one first. I'm in decent shape and work out 4-5 times a week but even still after a full day of swingin the Minelab and walking many miles on the beach I'm kinda wiped out.
But if you are going to do a lot of beach detecting the best is the excal II cause it's waterproof lets you get in the water and will take you to the real good stuff. Sorry you sold the ACE, could have kept that for the parks where you dont need to dig that deep.
But since you only want one machine, then get the Safari. I don't always look at the Display but is sure is nice to have when I want it.