own 4 and as stated above some just work a little better at some sites than others...and a little better can be the difference between full and empty pockets....presently own sov gt,whites 5900,excal 1000,gta 1000.....each machine has its strengths and weaknesses....if you have ever worked the same site over and over a long period of time you eventually realize no one machine does it all,,although some do a very good job the first time through no one machine gets it all....alot of these old homesites have a variety of foriegn matter in the soil such as coal ash,hot rocks,slag,in addition to the natural mineral content and trash....advertising often makes me curious about other units...if i was rich i would certainly own more of them just to satisfy my curiosity.........