I see you are stirring the pot hmmmmm?
The detectors mentioned are primarily coin, treasure and relic machines (VLF Discriminators).
The 2000 is a pain in the butt as a coin machine but yeah still good in the gold fields....for big stuff.
It will have you digging gigantic deep holes just to end up with a pick or horse shoe etc. Whereas a half descent VLF discriminator will tell you to not waste your energy cos it will ID the iron. The infinium is also very good at that once you know how to use the reverse disc. I have not used a GMT but I believe it is pretty good at giving a fair ID on ferrous stuff??
Out in the gold fields with any of the ML Pis you would be nuts to not dig every target, they do not miss much but as soon as you start to pick and choose your signals then that is when you will leave gold in the ground.