Both the DFX and Minelab are good top-of-the-line detectors. I think most everybody would agree that learning to use the detector is more important than the detector itself. Both the DFX and Minelab have a significant learning curve. Your experience with the DFX is typical for the first time out with any of the high-end detectors. I doubt if your experience with the Minelab will be any different. You need to pay close attention to what your detector tells you. This can be VDI number (or the tone assigned to it), conductivity, a signagraph, an icon "guess," or anything other information. When you first start, you won't know the difference bewteen crape and a good grade of clay. The information is just too confusing to know. You have to practice - dig, ID, remember; dig, ID, remember; dig, ID, remember; after a few months things will be much clearer and you can start to ignore targets you are sure of and dig ones you are sure of. The problem will be the signals in the "huge" middle that no detector can tell a significant difference in - gold, foil, nickels, pull-tabs - they all give signals that seem to be good ones but there will be more pull-tabs and foil unearthed than gold or nickels. If you are finding nickels, you are getting there. If you are "passing" on foil and pull tabs, you are missing gold. Just the way it works.
So set yourself up a good test plot. Practice, Practice, Practice. There may be quite a few DFX and Minelabs that are at the bottoms of lakes, or have bent shafts from being wrapped around a tree. I don't think anybody will fess up to this but I know I've had the urge. Digging bottle caps that ring at quarters, crushed beer cans that ring up as nice clean diggable signals, pull tabs that say "Gold Ring, Gold Ring, Gold Ring," WILL drive you nuts.
Have fun learning your new machine. Just don't expect miracles. It ain't gonna happen.
My 2cents worth.
Daryl