I went with OTHER because there are multiple mediums that I use, although the one that i use the most isn't even on the list.
MP3 - I rip CDs to mp3 to play in my car and on my phone. I have TONS of CDs, but they are cumbersome to carry around in a car (and always risk being damaged), so it's easier to throw music in a jump drive, pop into the USB port in the car and carry around thousands of songs in the palm of my hand.