Fudo

after playing both regular sun and ultra sun I can definitely say that there is pretty much no point in buying regular sun or moon if you only have the ultra. Pretty much all of the changes are late game and as you said its just a refined version of the original. One of the major things I noticed when comparing the two games was that ultra SM is much more streamlined and gets to the point faster than regular sun that kinda drags on and some island challenges have been improved to not be as boring as they were in regular SM. also ultra SM just has more content in general to enjoy.