Lots of great info here. I haven't read it all so I apologize if I am repeating something.
As far as the lenses and not the internals, good glass isn't usually just "clearer" than mediocre glass, to me at least. Its value lies in:
Signifigantly less eye strain when glassing for hours on end (this is (hopefully obviously) for binos and spotters only)
Much better low light performance
Much better clarity when dirt and grime, condensation, etc. starts collecting on the lenses
