These sound 'differences' are so subtle its hard to describe. I usually describe the sound of higher end caps, resistors, pots etc, as being more refined, mature, open, defined, cleaner etc. To try to get more specific than that is hard, and mostly relative to the current comparison, not necessarily generalizable to all situations.
Eric
Emotiva XPA-2, Magnepan MMG (mod), Quickie (mod), JRiver, Wyrd4sound uLink, Schiit Gungnir, JPS Digital power cord, MIT power cord, JPS Labs ultraconductor wire throughout, HSU sub. powered by Crown.