I was bored so I decided to type out my observations of one of my favourite tracks :)
I Want To Break Free
Perhaps one of the most brilliant remixes for single in the entire Queen catalog, this bouncy little throw-away number finds new life and major success when background synths are brought out, giving the track a more melancholy feel and extending the length with instrumental sections. Two basic building blocks for the remix exist within the album version. The remix's intro comes from background synth just before the electronic 'guitar' solo, and two key instrumental sections (only one remains in the single edit of the remix) are made from the final verse, minus the vocal. In the 'extended mix' the song carries on for quite awhile past the point where the album version fades out. This was probably how the song was originally recorded, going on for a while with Freddie doing some vocal ad-libs and such. I would imagine the song just basically broke down at some point without a proper ending and rather than fading the 'extended' version, they chose to do this 'More of that Jazz'-like compilation edit at the end.
Anyone with an ear for edits can tell the single version is an edit of the extended mix.. actually it's 3 edits and a fade. The first two are hidden well, occuring during the part where the drums first come in.. it simply edits twice from one snare to another to shorten it up by about 4 seconds total. Then where the extended mix goes into an insturmental 'verse' before the actual first verse, there is a semi-rough edit directly to the start of that vocal verse. You can easily hear the background music change with the echo of the instrumental verse still audible under Freddie's vocal starting. (Since there's no vocal to disguise it, this edit was re-done seamlessly for the karaoke version) Then of course the song fades to roughly the same point where the original album version did.
The 1991 Greatest Hits II single version fades a few seconds earlier than usual, with an actual audible time of 4:17 compared to 4:21 on the U.S. 'Greatest Hits')
The 1992 12" Collection version clearly runs a bit slow, resulting in a run time of about 7:19 compared to 7:11 on the Hollywood 'Works' CD. I did comparisons of exact sections of the song from various sources to confirm which was correct.. and the 12" Collection version begins to lag behind and always runs slower than all other versions even within a small section, so it is reasonable to say that this version is mastered too slow.
The karaoke version runs only about 4:12 because the original karaoke flix video it was made to match was this length, fading in a bit late and out a bit early, as videos often do. This was not corrected on the 2004 remaster.
The album version sounds like it might run a bit faster than the remix, however in comparing the first verse from each, it comes to within one frame or only about 100 milliseconds different.
On a personal note, I really like long songs and I love this one, so my preference is for the extended mix. However, I do find the little medley edit at the end very annoying, so I often fade the song out to about 6:04 just before this starts, for compilations and such.