My comparison of the two detectors? I'll try to keep it short.
Well, I loved my Explorer XS's ability to find coins deep and to get good targets that were with or adjacent to rusty nails and iron.
I was using conductive tones and a very low Iron Mask setting. I hunted primarily by sound. The rest I left up to cursor behavior and position. I really liked the sound.
Pinpointing was a little hard to start with coming from using concentric coils since 1985, but I learned how to X my targets to optimize pinpointing at depth. Not long after acquiring my XS in 2000, I was fortunate to get a Sun Ray X-1 pin pointer. I don't know how I lived without one before. It make recovery quick and easy.
Earlier this year I decided to try my hand at an E-trac. The difference?
Lighter
Better hand position, it is more up and down rather than my hand tilting forward.
Simplified pinpointing, more accurate for me and no need to X the target unless I want to
Even better depth than my XS
Pro coil is lighter and seems more sensitive
New screen orientation (X,Y) and increasing of conductivity scale 0-50. I like the new screen layout better.
Seeing both the graph and the smaller digital scale (kind of like picture in picture) is a big help as I analyze a possible target
There is a 1/4" headphone jack.
Still a problem that they haven't fixed?
Yes;
1. The V shaped arm cup is still wrong. Still have to go aftermarket there.
2. It would be nice if it were rain and splash resistant.
3. It could be even lighter
4. Hand grip could still be better. I'm seeing a lot of electrical tape jobs and tennis racket grip and handlebar tape.
Those points aside, I still like love the E-trac and it's ease of use. There are settings to tweak, but not so many that one gets lost and isn't sure which way to turn.
The Explorer lineup is actually pretty easy to learn and become accomplished with. Becoming an expert still takes time behind the display and out in the field, but a person can take an older XS or a brand new E-trac and shortly be recovering deep targets in relatively easy fashion. I think that is why the Explorer's in general have been so successful and we see so many success photos and stories on this and the E-trac forum.
I'm sure that others can add to the list of improvements that have been made to the original XS as it has evolved to the Explorer II, SE and now SE Pro.
Good luck
Rich (Utah)