I have a gmt, a lobo supertraq ,a diablo gold deamon2 and a diablo umax. The umax is by far my favorite machine,the gmt seems noisy and confusing to me,the supertraq is smooth but you have to have the threashold up to high and you cant manually ground balance the machine. The gold deamon2 does not have the power of the diablo umax.The diablo umax is incredable smooth, deep, you can lower the threshold down to the tiniest hum and it stays contsant, where the gmt and the supertraq threashold will disapear.I love manual ground balance ,I dont trust tracking.The diablo is so easy to ground balance and with two ground balance nobs you can do so many things with it,have one spot on and have the other one negative for an alkali patch or one spot on and the other a little positive for checking out the small or weak signals.I just wish it had a 180 disciminator like the lobo supertraq.I cant wait to take it out west to see what it can really do, and compare it to the gmt.