Well, I am going to go and support the DFX and here's why. You can adjust your DFX to perform equally to the MXT if you take the time to learn it. Your coil options are the same, you can run the DFX in 15kHz only (about the same as the MXT which runs 14kHz, I believe) and make adjustments to filters, sweep speed and recovery speed to mimick the MXT. Then, when your done prospecting, you can go coin shooting with just a few more adjustments.
By the way, neither is "excellent" for prospecting for gold. For that you would need a machine that will run at 50kHz or above.
Also, if prospecting and you want to find smaller pieces of gold, or deeper coins for that matter, be sure to use AA alkaline batteries verse the rechargeable battery pack. The machines work way better running between 12+volts and 11.0 volts. The rechargeables will start in the mid 11volt range and quickly drop into the mid 10volt range and stay there forever, the problem is you are losing valuable sensativity by detecting with a charge under 11 volts.