Have both the CTX and E-Trac and have tested them side-by-side and in the field. The CTX has a slight edge on depth, target separation, unmasking, and providing visual and audio information. The caveat is that the CTX isn't a "wow" factor upgrade, it isn't a major leap in technology, more of a tweak. You might get that fringe area target in and around iron that the E-Trac would null on at depth.
The CTX color screen is nice - but washed out and hard to see outdoors. Most hunt by audio clues anyway and glance at the screen to confirm. It would have been nice if the screen pivoted - turning it toward the user, but it doesn't.
The useful thing about CTX's combined mode is that the split bottom zone (bin) can be assigned a Low Tone audio without using DISC. This one feature allows the use of zero DISC in 4TF which helps improve target sensitivity and depth. So, that's a plus.
The majority of the weight of the CTX is behind the armrest and allows the stem to pivot at the grip- which is a natural balance point. That is, there is less felt weight even though the CTX is heavier than the E-Trac. The net effect: it is easier to manipulate and there is less torque on the arm - which is less tiring.
Both the CTX and E-Trac are low freq machines and are going to be silver sensitive - which if you are a coin hunter is a plus. They both have great TID at depth - though the CTX has a slight advantage there. The CTX may gain 1/2" to 1" more accurate TID depth over the E-Trac, depending on soil characteristics.
If you are going to buy an FBS machine - it would make sense to get a used CTX rather than a new E-Trac, both run about the same price. If you don't need the TID and just want to know if a target is non-ferrous or ferrous at depth, there are cheaper solutions.