Unless you're listening to classical music with an incredibly trained ear (eg you played it) then you won't notice a difference between the tracks.

That's my professional opinion as a sound designer. Personally I like the best compression bang for my buck. So it's m4a at 192 kbps. For compatability mp3 will do just nicely at 192 kbps.

If it's for your glove compartment nano then use m4a. :p

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-Typos courtesy of my mobile phone.