I was in sixth grade when the recording of Cliburn playing the Tchaikovsky 1st and the Rachmaninov 3rd was released, flip sides of one record.
I had already been given the live performance of Horowitz with Toscanini, and when a friend of mine talked about how great Cliburn was, I thought it was pure bunk. And the Rachmaninov 3rd seemed so slow in comparison to what I had heard. I remember one particular mistake in the first movement cadenza, and at that time I thought great pianists played perfectly. I also was not much impressed with the recording itself, the sound.
I was young, naive and used to studio recordings.

From time to time I've returned to this recording, and I now very much enjoy this live performance, mistakes and all. The mistakes are really very minor (there is a particularly noticeably mistake by the lead trumpet in the 3rd movement, so I think the orchestra under Kondrashin was nervous!). But now the imperfections just make it more human to me, and those hearing the perfomance live, even if they heard mistakes, would not have cared. Also, just think how few pianists played that work then.
Today I understand weird things happen live. I have another recording of Agerich playing the Tchaikovsky Bb that I think she might have tried to block, because the 3rd movement starts out with some mistakes that we would normally expect from lesser pianists. But from that point on, the whole performance just "smokes", a total adrenalin high, with the lady playing just on the edge of disaster and enough heart for players. I just love this live recording. In fact, the whole performance bears some amazing similarities to the Horowitz/Tocanini recording, but the slow movement is much slower and more thoughtful, which I think is wonderful.
I love the Cliburn Rachmaninov 3rd recording for another reason. For me it has warmth and character that makes it unique. Each time I hear it now, I think how stupid I was when I was young.

However, the flip side (the Tchaikovsky 1st) is a different matter. I was told that Cliburn was so intent on a note-perfect studio recording of the Tchaikovsky that all the heart went out of it because of too many takes. Certainly this is quite possible. I've always suspected that live performances, during the Moscow Competition, were probably less accurate but much more inspired. Just a guess. Live is so differernt. I have never been blown away by anything Ashkenazy has recorded, but I heard him play the 2nd and 4th Beethoven Concertos in Miami, and I was totally enchanged by his playing. In addition, it was the most accurate live performance I've ever heard. Somewhere he partially "brushed" an adjacent key. Except for that, I believe that performance could have been released and passed for a studio recording, if crowd noise could have been "magically" eliminated.
Like some people in this thread, I once thought Cliburn was the product of political hype. But long ago I changed my mind.

Gaer