The Gold is probably the best but very expensive and takes a lot of time to learn.
Of three you listed, I'd go with the Detectorpro with the 8" coil.
The Dual Field with its 12" coil is like swinging a garbage can lid and pinpointing is a nightmare. I know. I owned one.
Sold it and got the Detectorpro. It's amazingly lightweight and you can swing it all day, something I cannot say of any other beach detector. Pinpointing is dead on and the depth is amazing. I'm just sorry I didn't find it sooner.
It's very powerful so be warned, you will dig deep targets so get a decent sand scoop. Also, it drinks those 9 volt batteries, and forget rechargables. Alkalines will get about 8 hours of use to a pair. And use the Energizers. For some reason, they're the only ones that really last.