LR,
MP3 is a much lower quality storage mechanism than CD, due to the high (and lossy) compression. If you are an audiophile, be aware of this - don't expect too much from MP3s.
Put it this way - how many music CDs can you fit on a music CD? One. Now how many MP3s can you fit on a CD?
I rest my case
Convenient? - yes! Quality? - no.
SD