When you hear that riff Da da da, Da da da, Da da da , Chord..you feel the pulse on each of the Da da da's, which to me would represent each one of the da's as a quarter note. If it was in 9/8 you would only feel the pulse on the 1st Da, which would make it a much slower tempo.
Ex:
|9/8 Da da da Da da da Da da da|12/8 (chord)......||
So in 9/8 all of that would take place within 2 measures
|3/4 Da da da | Da da da | Da da da |Chord (4 measures)
3/4 represents a much faster tempo and a heavier emphasis on each one of the da's.
