There is no difference in learning the CTX or E-TRAC, and in fact if anything, the CTX menu makes more sense and is easier to navigate.
A few key differences to me in favour of the CTX
1 - pin-point (and back) button - just makes everything so much quicker
2 - target trace
3 - wireless module - never have to worry about broken headphone leads
4 - far better balance. The CTX armrest and handle also feel much better
5 - being able to just hose it down after a beach hunt is great
6 - The semi-auto ground balance
7 - Combine, and being able to set whatever tone you want for different targets!