I can tell you that at least for me it all comes down to coil choice as to which has what edge on what. I've seen what a good coil can do in both depth and separation. There are many excellent aftermarket coils for the Explorer, and there are many for the Excal (or Sovereign), but if you don't have a waterproof plug on your Excal to change coils but you do have some good aftermarket coils for your Explorer, then right there is your answer probably.
Just the same, don't take the advice of others when you have both machines to play with on that beach. Test them both on gold and silver yourself to see how they do against each other for what you're after in that sand. Nobody better than your own eyes and ears to tell you which to use for what on that beach, because nobody has your soil or sand, and that could make the difference between which does what for you.
Take a few gold rings (or better yet gold coins since that's what your after) and a few silver coins to the beach and bury and also tip a few on edge and then start to play with both machines and see if one's coil or it's unique traits handles your sand minerals better than the other on those targets. Just tie a string to all of those targets so you don't have to worry about losing them being buried too far. Keep sticking them deeper until one machine can hit them and the other can't. That's when the edge of which will do what in that sand will tell you which machine might be better than the other in that particular beach on those particular targets. All this stuff can change from beach to beach IMO. Also, try your Excal in PP mode and see if that pushes things even deeper. Who better to give you the final word then you and your particular beach with both machines?