No, M3U is simply a playlist, whereas a cue sheet describes the exact position of each track on a disc, as well as subcode informatino, if desired. Remember, there are no physical tracks on a CD, it's just one long data stream. Cuesheets are what tell it where the tracks are. Here's examples from my personal collection...
M3U
Guns 'N Roses - Civil War.mp3
Metallica - Welcome Home (Sanitarium).mp3
Nirvana - All Apologies.mp3
P.O.D. - Set it Off (Tweaker Remix).mp3
Edgar Winter Group - Frankenstein.mp3
Jimi Hendrix - Foxy Lady.mp3
CUE
CATALOG 0075596274227
PERFORMER "Dream Theater"
TITLE "Six Degrees Of Inner Turbulence (Disc I)"
REM REPLAYGAIN_ALBUM_GAIN -8.55 dB
REM REPLAYGAIN_ALBUM_PEAK 0.999969
FILE "Dream Theater - Six Degrees Of Inner Turbulence (Disc I).flac" WAVE
TRACK 01 AUDIO
TITLE "The Glass Prison"
PERFORMER "Dream Theater"
ISRC USEE10140472
INDEX 01 00:00:00
REM REPLAYGAIN_TRACK_GAIN -8.28 dB
REM REPLAYGAIN_TRACK_PEAK 0.999969
As you can see, a cue sheet contains much more than just track names. It has a catalog number of the CD, the artist name/album title/song titles, replaygain information, ISRC information, and the actual position of the track, located in index. Note that most of these are optional; the only thing neccesary for playback is the index. The only thing that actually changes the sound out of these is the replaygain, which just brings the volume of the disc down. (to an attempted 89dB RMS)
(-:Stephonovich