Thanks. Can we know a few tittles of the LPs you are referring as your better pressings? It will be of real help to put a perspective in your findings.
mostly Lps i used for my references back in 2000-2002 were my early 45rpm reissues, which i still use as references. some of the specific cuts i used then are;
"Satin Doll", Blues a Plenty, Johnny Hodges, Classic 45rpm 4 disc
"Take 5", Time Out, Dave Brubeck, Classic 45rpm 4 disc
"Misty", Ella, Let No Man Write My Epitaph, Classic 45rpm 2 disc.
"Day in and Day Out", Billie, Songs of Distingue Lovers', 45 rpm 2 disc.
'"Malletoba Spank", Duke, 'Jazz Party in Stereo' 45rpm 4 disc.
"St. james Infirmary", Louis, Satchmo Plays King Oliver, 45rpm special pressing.
"Scheherazade", 2nd movement, Classic 45rpm 4 disc
"Faust", Funeral March, Gibson, Classic 45rpm 4 disc.
"Helplessly Hoping", CS&N, Classic 45 rpm 4 disc.
there were many more, but these are a few of the ones still in frequent use as a reference. and i can hear how these cuts have progressed over the years.