compared to persian classical music, there are less notes in it because persian music uses notes "between" the 12 notes of the western system... but that's not quite right either because classical does use a mix of different tuning systems, we just dont give the notes different names when we do it.
compared to carnatic classical music, the rhythm is much less complex.
mozart was known for syncopation, but certainly not a lot of isorhythm or polyrhythm.
but thats talking about western classical from a long time ago...
classical music is still being written!
and today, the composers in all these styles are aware of and influenced by each other.
so todays "western classical tradition" composers do use microtones and polyrhythms.
and i know chinese classical tradition was influenced by western tradition in that they started making larger and smaller versions of their string instrument to mimic the way the violin family has basses cellos violas and violins.
you know... i think the system you know the most about will always seem the most complex to you, because you are not aware of all the complexities if you only know a little about it...
so there arent many objective people who are experts in multiple classical styles.
so i suspect they are all equally complex, but they have put their complexity into very different elements of the music.