MFSL Gold cd or Current Japanese CD?

A blanket statement would be meaningless as there are just too many variables.
IMO: Your question would best be answered on a title by title basis and even then it would be difficult.
The Japanese releases could number 6 or more versions from the date you mentioned, some re-mastered, possibly more than once.
In the case of SHM-CDs, there's already 2 or 3 versions on several titles in the short time they've been available.
Some MFSL CDs have also been released several times, once by the original company and then by its buyer, Music Direct.
Santana's Abraxas comes to mind.
There's also HQCD, XRCD and Blu-spec CD.
So to compare some specific titles may involve listening to 10, 12 or more CDs. I'm sure it could be done but it wouldn't be easy.

Lenny,
I guess you have your answer. Sometimes I do wish it was that simple.
BTW: There are very few K2HDs available. I had one, I personally didn't like it much.
As far as XRCD, there are XRCDs, XRCD2s and XRCD24s. Also, there are "old" Mofis (Mobile Fidelity Sound Labs) released by the original Mofi and "new" Mofis released by its current owner (Music Direct). Also, you didn't mention DCC (Dunhill Compact Classics) which also released some fine sounding CDs.
Argyro,
Could you clarify what you mean by "I have ALL the recordings from these companies..."?