the first difference is money.the gold bug went for around 600.00,has been replaced by the gold bug II. not sure what it go`s for now?,the gold bugs are great for nuggets,coins,rings,eck.
the 1280x is for under water use,and detects deeper.sells in the area of 1,200.00 or more.
the minelab is the cats meow,for deep targets.lists for over 3,000.00
i like the 1280x because i can use it in the rain and saltwater,its good to 200 feet down in saltwater.