yes, upped non-eth is similar to non-upped eth. however, the defensive range is generally disliked.
when unique items get an enhanced defense mod, the BASE defense BEFORE the %bonus is always standardized at the maximum of the "normal" version of the base armor +1. for example, arreat's face (in its original non-upgraded form) has a range of +150-200% enhanced defense. while a slayer guard (the base exceptional item) has a defensive range of 93-120, blizzard decided to make it simpler and just set the base defense on arreat's face 121 (one more than the original maximum, 120). therefore the final defense range on exceptional arreat's face is 302-363 (121*2.5=302, 121*3=363).
however, when upgraded, this "maximum def +1" standard disappears. ethereal armors also lose their inherent 50% base defense bonus when upgraded, so getting an ethereal item and upgrading it is pointless -- you'd be getting the same if you upgraded a non-eth item.
so let's say you upgrade a non-eth arreat's. a guardian crown (elite slayer guard) has a defense range of 117-168. so the final minimum and maximum defense of upgraded:
117*2.5=292
168*3=504
now for the minimum and maximum of an ethereal, non-upgraded arreat's:
121*1.5*2.5=453
121*1.5*3=544
as we can see, the defense of non-upped eth arreat's is better, but it is much more expensive, and also requires a zod rune (unless it's bugged, which is a whole other story). upgraded items also have much higher requirements.
hope this cleared up something.