The great thing about that is, the original album that brought the Allmans so much acclaim is as notable for its clever studio editing as it is for its performances. Producer Tom Dowd skillfully trimmed some of the performances down to relatively concise running time (edits later restored on the double-disc set The Fillmore Concerts), at times condensing several performances into one track.
I haven't (yet) lined up both discs side by side for their entirety, but the only significant difference in timing I see is on Stormy Monday - the DE lists 8:48, while TFC lists 10:19.
Then, they say this about TFC:
It is also a slightly less honest release, where "In Memory of Elizabeth Reed" is concerned -- Dowd edited the version here together from two different performances, first and second shows, the dividing line being where Duane Allman's solo comes in. Not that this is the only concert album where this kind of editing has been done, but the original Live at the Fillmore contained a single take of the song, and some purists may prefer that.
Again, I haven't played the two back in perfect sync yet, but the last time I listened they seemed to match. What gives?
I'd say I prefer the original mixes (the remixes have some added reverb that isn't necessary), but I do like the fact that TFC doesn't fade out between tracks, something that's kind of annoying on the DE.