I went down the Explorer route for that exact reason, the very useful iron/conductivity ID's, and to get an edge depth wise over my other detectors. My budget was limited, so Etrac was out of the question, and the ctx was definitely a no go, and even if I could have afforded those two detectors, I would still find it hard to justify the purchase price in the first place. I also wanted an FBS detector for effective beach/wet sand detctecting
I wanted to be able still detect in purely all-metal mode for deeper targets, but have the flexibility of using various features and settings to aid target identification. As per the Etrac, you can use either the smartfind screen or the digital ID numbers to check the physical properties of the target, and the depth meter should help indicate the age of the item (assuming older items will sit deeper than the more modern junk). The bonus is that you get all this info without having to resort to using any discrimination, hence no nulling and p less masking of targets.
Whilst I love using the G2 in trashy ground with its effective discrimination and ultra fast recovery times, it is ultimately limited in depth, and running in all-metal is not doable due to the sensitivity/high kHz picking up too many unwanted targets. That is when I usually grab the Explorer to search for the deeper targets.
I'm sure either the Etrac or CTX should fulfill that role quite well, it's really down to budget, or whether you feel waterproofing, gps, and some other improved/added features are worth paying a premium for over the Etrac. Also keep in mind that the Etrac has more coil options over the CTX.