If you like music videos and songs, you not not need to buy both from itune, just buy the music video and then transfer it to the video playlists and the music playlist and it will play audio when playing from the music list

I sometimes put the Nano in random play and let it select its own order of my 500 favorite songs

The song will play fine on iTunes but not in the Nano

she will never run out of room for her favorite songs.

If you want to watch videos, then of course the 4G is better.