"Best" at what? Best for hunting gold nuggets? Or strictly a coin shooter? Best water machine? There will be many bests.
I'm 75 and have been detecting for something like 50 years. My first detector (back in early 70's?) was a Judge. As you suggested, many detectors over the years, and to me, to pick "the best" would be a pretty tough assignment. The best one I've had (and still have), for silver hunting, and really most other targets, would be the Sovereign GT. Excellent on the dry and wet sand beach as well. But only after learning the subtle sounds she whispers to me as she glides over a target. A bit heavy. But goes deep, and doesn't miss much.
I've had several Fisher CZ detectors, and they have been excellent on the beach and in the ocean. Hip-mounted, super easy to use, and rings loud and clear. A Minelab underwater machine may be better, but the CZ-20/21 is definitely more durable. You could stand on the control box, and not hurt it. Minelab is a fragile machine prone to many failures. Which one is the best?
My wife has been hunting with me for nearly 20 years, and she's good. She is small-frame person, and wants/needs a light-weight machine. I've had her try many machines, from Etracs, Xterra 705, CZ-20, several Fisher F-series, many Garretts, Simplex+, etc, and she will be quick to say "the best" detector is her Tesoro.... uncomplicated, tough and very light weight. With nearly a dozen machines to choose from, it is the only one she wants to use. I keep going back to the Sovereign.