You do not mention if it is the later 5000 or the earlier 4000 UWA you are referring to, but your mentioning of small size indicates that it is the older 4000 UWAs(?). I have the current ES 4.7mm and 6.7mm as well as the old Japan made Meade 4000 UWA in in the same focal lengths.
I have used them head to head just a few times and plan to do a more thorough comparison with a write-up later. My initial impressions are that they are optically on the same level. The big advantage of the 4000s over the 5000s and ESs is the tiny sizes of the 4.7mm and 6.7mm focal lengths. The big advantage of the ESs is the ergonomics. With the 4000s you need to put your eye straight up to the eye lens and even then you have to move your head and "peak around the corner" in order to take the whole field. The ESs, in contrast, provides a big easy panoramic view. I know some people complain about the eye relief of the ES82s (and the Nagler T6) with reference to the big easy panoramic of view of a XW, Delos, Morpehus etc. It is kind of the same feeling switching from the 4000s to the current ESs.
Edited by dufay, 07 February 2017 - 12:00 PM.