From my experience the UX Dacron is way softer and easier to fold. I fly UX and standard kites back to back all the time and I see how struts bend when I'm infating the kites and how much easier it is to fold the UX material.
I can not comment on the LE diameter as I don't have same model&size kites in the 2 different constructions, but my feeling is that UX does not have thinner LE for its size. I compare my 9m Enduro V4 to 9m Alpha UX and my 6&7m Reos.
But as you wrote - these are fantastic kites! If you love the Reo, try Alpha UX in the bigger sizes, I'm currently torn to say which is better for waves in underpowered conditions