i am with loz on this one. "classical" or to be more accurate, western art music. A. there is a much larger playlist available (it would take a good portion of your life to listen to all of bach's work alone) B. i feel it is much more diverse a listening experiance.
having to choose one piece alone, not a chance. although in classical, my current favourite is Carl Orff's Carmina burana. (saw it the other day. orchestra and four choir's,soprano,tenor and contra-tenor. there were as many performers as audience.)
but in the real world, who can choose one brand of music? me, i love playing blues slide guitar, and i love playing a bit o improv jazzy funky stuff on my classical beater. i have my dirty great electric to rock out with. add in the keyboards, the software synths, argh!! so much possibility!! its great