How they differ from each other is the nature of the splice.
#1a - Dukas, The Sorcerer's Apprentice, measures 913-919
#1b - Dukas, The Sorcerer's Apprentice, measures 54-94
The two clips are from the same piece, but in the wrong order. The music representing the master sorcerer quieting the brooms for good is followed by their coming to life to the first time.
#2a - Brahms, Symphony #2, 2nd mvmt, measures 86-91
#2b - Brahms, Symphony #4, 2nd mvmt, measures 84-87
The two clips are from two different pieces. Both selections are from the same dramatic point in the slow movement, the transition theme to the final appearance of the second theme. I'd figured that this selection would give away the nature of the splicing; the change from slow 4 to slow 3 is rare for Brahms, and even rarer is the first clip with the timpani in F# and B and the second clip with them in B and E, as Brahms in his symphonies asked only once for a retuning in the middle of a movement (sym 3 ; first mvmt) and only once used three timpani (sym 4 ; third mvmt).
#3a - Beethoven, Symphony #3, 1st mvmt, measures 33-56
#3b - Beethoven, Symphony #3, 1st mvmt, measures 83-94
The two clips are from the same piece and in the right order, making it a simple cut. This is a recreation of a passage from one of Leonard Bernstein's lectures exploring Beethoven's notebooks, this was an earlier version of this passage. Beethoven later added the two energetic sections in measures 57-82 before settling in the second theme for good.