I don't own X1E, but I do own fully specd up X1C. Screen on this thing is way better then on any Dell laptop, it feels and looks like an Amoled straight from Samsung. And X1E 4K uses the same screen. FHD version is way worse then on Dell laptop. You can swap fn and ctrl keys easily.
Looking at reviews, Dells 9570 has really bad thermals. Not MBP bad, but not good also. X1E seems to be better in that department. Not personal experience, just judging by mostly youtube reviews.
Only thing where dell surely wins is battery life.
And yes, X1E does cost more. But you get better ports, way better build quality, and probably the best keyboard out there. For me just the keyboard part is worth the price, build quality is just icing on the cake