I think there is a degree of truth and sanity in Macca's post.
A number of things come to mind. When I rip a CD to my NAS I am convinced the streamed music sounds better than the original CD, it shoudnt but it does!
Many so called Hi-Rez downloads are taken from a 16/44.1 files and upscaled. That is NOT Hi-Rez. This has been proved by a number of Hi Fi magazines. HiFi News now test downloads (somehow) and give the results.
SACD has a smoother sound IMO but I also have a number of SACD's which sound no different to the original CD (Blood,Sweat & Tears 3 and Abraxas come to mind) which could easily be down to mastering.
I think the jury is probably still out on this one and opinions will go back and forth for an eternity. Please don't start me on BluRay 24/96 files of which I have a number.
Clive