Personaly if I were to use Ogg Vorbis it would be at q6, it's a fair balance between quality and file size.
Don't discount the other formats yet though, bear in mind that MP3 is still the most widely compatible format for use with just about anything.
While WMA proports to give equal quality at lesser file sizes.
It comes down to your own choice really, try a few formats/ settings out and choose whatever your happy with. Just don't get to caught up in it and stop paying attention to whats really important,
listening to your music 