Mineralized soil, wet salt sand, mild to moderate trash, looking for older coins and mid sized to larger gold rings....E-Trac
Milder soil, moderate to trashy sites, old coins, gold jewelry hunting of all types except micro gold, nugget hunting....X-Terra
I have both units and they do compliment each other, but I find I am using the X-Terra more simply because it's easier to use, lighter, and is hotter on gold jewelry with the HF coil. Both units do well in iron, but the E-Trac with the way it can run and how it has both conductive and ferrous ID, is better at IDing in iron laden sites. But the X-Terra with the LF Digger coil is a killer in iron too and a super silver coin hunter.
E-Trac is an awesome unit but it is becoming heavy on the arm for me and I only use the Sunray X-5 on it now for old silver coin hunting. Got the Pro Coil and Sunray X-8 for it but I can't swing that baby for long even with the 8 inch coil on it.
She may be going up for sale shortly.
Don't sell that X-Terra short....it can hunt with the biggest and baddest of detectors and the only place I find it can't keep up, depth and stability wise, is on a salt water beach ( but I stopped using my E-Trac in that environment due to I have water proof units for that, and it was almost toast one day when a big wave hit me in the wet sand and splashed up and almost drenched the thing. No more of that ! ) The X-Terra in the wet salt sand does well with the LF coil in a pinch
I don't hunt places with highly mineralized soil so I cannot comment first hand on how the X-Terra does, but based on reading and experiences of others, it seems the E-Trac is the better unit in that type of condition,
Good luck if you decide to get an E-Trac...you will have fun with it.