First off what type of hunting are you going to be doing, freshwater/saltwater or both?
Do you want depth with discrimination with sensitivity to small gold?
Generally this is the Order of Choice gathered after reading the forums for years and owning a number of them.
VLF machines
Freshwater only:
Tesoro TigerShark
Fisher 1280x or Detectorpro Wader
White's units
Saltwater only:
Excalibur
Fisher CZ20-21
Fisher 1280 or DP Wader
White's units
FRESH & SALT
Excalibur
Fisher CZ20-21
Fisher 1280 or DP Wader
Tesoro TS
White's units
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Ultimate depth in Fresh and Saltwater, PI machines ability to handle all soils, NO DISCRIMINATION. You dig it all.
Commonly used PI detectors in order
Garrett Infinuim
Detectorpro PI
White's Surfmaster PI Pro Duo
Whites Surfmaster PI PRO
Tesoro Sand Shark
Garrett Seahunter Mark II (claimed discrimination)
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Overall the Minelab Excalibur is the #1 detector and the
CZ20-21 follows as second if you need a detector to cover fresh and salt.
Pulse machines are the best for sites not laced with iron and junk metal. They find it all to extreme depths, you can chase a hairpin at 15".........and there are pulse units that are even better than the Garrett Infinium but, only used by those that can afford them. I'd rather have a newer car....LOL
You need this ultimate combination to cover all conditions:
Tesoro Tigershark
Minelab Excalibur
PI
Hope this helps.