I'm using Dell Inspiron 7000 2-in-1 7391 with the FHD Touchscreen panel (Chi Mei CMN1384) for a couple of weeks now. Between trying the XPS 13 with the FHD matte panel, I tried the XPS 15 with the FHD matte panel. The XPS 15 was the most painful of them all, I think mostly because it was very bright even at its lowest setting (as well as using PWM below 26%).
I like the Inspiron, I am keeping it. Better than the E7450. The panel, despite seeming reasonably comfortable so far, is actually really terrible from a PQ standpoint. Everything looks yellow and the colours are way off. I don't really care though as I don't do any work that requires accuracy.
I would rank them: Inspiron 7391 FHD Touch > Latitude E7450 FHD > XPS 13 9380 FHD Matte non-Touch > XPS 15 7590 FHD Matte non-Touch