My Superdisc copy of Styx's Pieces of Eight (which, amazingly, I got sealed) sounds absolutely stunning. Leaps and bounds better than my standard copy, one of the best sounding records in my collection. Sounds like the band is playing right in front of you.
My sister has the Superdisc press of FM's Rumours. As far as I remember, it sounded pretty good, but nothing incredible. Better than the standard OG press. So some titles are likely better than others.