Which "Kind of Blue". I'm so confused

If you have a SACD player, go for the hybrid multi channel SACD. It has the three original mono tracks corrected for the problem that was in all the original vinyl and red book cds. It does not get any better for Blue then the multi channel SACD, I have all the issues: vinyl, reel to reel, Cd and SACD and nothing beats the SACD multi.

The sessions were recorded at the wrong speed (too fast) and the problem was not identified and corrected until they found the safety copy of the master tape in the 1990's. The 1997 Columbia reissue features the corrected speed, as do the other reissues after that date. There have been many LP reissues, some of which feature versions of the album at both speeds.

In short, pick up something post-1997.

That is an interesting dilemma. This is one of the most famous jazz recordings ever. The recording at the wrong speed is the one that made it famous. If it ain't broke don't fix it.

By fixing it they have basically slightly changed the tempi and the pitch. But people loved it the way it was.

If the "error" was never discovered, who would have really cared? It would be different if the recording originally bombed before they fixed it.

That was kind of my point. I was aware of the speed issue, but it never meant much to me.

No one a the time (musician's & engineers) picked up on the error by ear when they heard it. These kind of people have fantastic hearing. So how much different is it?

A reissue might sell a few hundred thousand copies. If they tell everyone they fixed a mistake, they can sell millions of new copies. Am I giving away a trade secret?

So will your wife care if you only spend $5 for a used CD made before 1997 instead of $30 for the latest thing?

Buy the remaster if you care about sound at all. Remasters are not just for "hardcore". Most are a great improvement.