There's several XP's went across to the States but the ground is hotter in general than in the U.K. so they didn't do to well.
The Goldmaxx Mk1 is legal as long as not fitted with the wireless headphones. The Goldmaxx Power isn't.
The Mk 1 is slightly less fast as far as recovery speed is concerned but in general with detectors the faster the recovery speed the less the depth so XP did well getting a little more depth out of the Power. Interestingly recovery speed was considered all with the high frequency XP's but when the F75 came out with its fast recovery it was described as "overcooked" Optimising to pick up tiny/thin coins is at the cost of larger and thicker items.
The Mk 1 has two detecting modes. Full range discrimination and iron only reject.
The Power doesn't have the full range discrimination only iron "level" reject.
Both lack true ground balance though there is ground adjustment knob which appears to use a degree of discrimination against ground minerals.
Wet beach performance is terrible. Directly the sand gets damp the response from a target goes down to the size of a pinhead and depth drops. I do use mine for the narrow dry top strip of beach where there's lots of iron but also small silver three and six pence coins with the odd ring mixed in.
The Nexus models are very deep detectors but again the U.S. soil causes more problems than over here. Base model machines from C-Scope like the 660 can outperform more expensive motion machines. Lots still buy the lower range models from Viking that have no discrimination as such except an inbuilt degree of iron rejection. Non-motion but iron see-through like the old and famous Compass 77b.
Unfortunately there's never been more brainwashing in the detector world than now.
