This appears to be the longer cut. There are three cuts: one is about 62 minutes (the TCM cut), another is 47 minutes (the French TV cut), and the one IMDB lists for the USA is 58 minutes. To confuse things further, we have the issue of PAL speedup.
However, the cut on YouTube is the TCM cut (you can see the TCM logo at one point in the later parts). And, there are some interesting differences between it and the Connoisseur Video version that I have. First of all, the Connoisseur Video has the PAL speedup issue: at certain points, Welles sounds as if he has just inhaled from a helium balloon.
But differences in content are also present - very interesting ones! They all occur, as far as I can see, in the section of the film covered by the YouTube "Part 1." All the changes are intended to speed the first part of the movie along. The first is the transition to the men talking in the street about Mr. Clay's ruined partner. On the YT/TCM cut, they have a longer conversation. On the CV cut, Welles adds some narration and the men's conversation begins with the line, "There would be a little matter of 300 guineas." (Also the transition shot showing the men, or at least two of them, for the first time, is reduced to a very rapid shot.)
Another change is that material from the Clay-Levinsky-cricket conversation (

) is cut. For example, Mr. Clay's request that Levinsky repeat part of the prophecy (on the veranda) is cut. Some material prolonging Levinsky's astonishment at his new assignment is cut. And strangest of all, Welles's wonderful narrative voiceover lines "But he had been thinking it over...He thought this old man was going mad. He knew he held Mr. Clay's fate in his hands" etc. (I am paraphrasing) are cut completely. Instead, Levinsky leaves the veranda for the second time, glances at Mr. Clay, and closes the gate all in total silence; then we cut to his walk home and Welles's voiceover line, "This clerk could have been a dangerous person...."
Which cut is the true Welles cut? I opt for my CV cut (which appears to be the 58 minute USA cut sped up by PAL to about 54 minutes). It's faster, points of exposition in the first part are made with greater alacrity, and as such it feels more in line with Welles's previous movies (though it is still slow-moving).
A gorgeous movie. Isn't the Satie music wonderful and moving, especially in the end titles? And aren't Welles's supporting players terrific?