If you look at your Smart Find screen quite a bit it will be a difference.
The XS was the First Generation processor. The SE/SE-Pro is the Third Generation as far as how fast it will process information and relay it to the Smart Find screen.
As far as depth: I cannot say on a definitive note because I sold my XS and then got a XS-S then got a XS-II back over 10 years ago.
I never got to to do a side by side from a XS to an SE only a XS-II too an SE and SE-Pro.
As far as side by side for the XS-II
NO you will not see any increase in depth but, you may very well like the newer features the SE offers.
Many like the VCO pinpoint and the ID in Pin-Point mode but, for me it really does not matter.
As far as depth: Sure I can slap on a WOT coil but, that is what is giving me the extra depth NOT whether it is an XS-II or a SE-Pro. I rarely even use anything other then stock coils although I have some coils (small and big) just collecting dust.
You can ask 10 people which they prefer more. Remember to take it with a grain of salt because, you will get many different answers. The same goes for Coils, Headphones etc etc. fwiw.
I will also add you might already know ML does not appear to be servicing/replacing the Circuit Boards on the XS so, that is a plus for getting the SE.
Hope I helped!
Edit: I have no definitve proof but, I do feel from the XS-II and later the Audio Circuitry is better and offers a cleaner/crisper sound.