Well, the first question to ask is where you will use the music, and what for.
General consensus around here has been:
- If quality is your chief concern, then re-rip to APE (or FLAC), both are lossless compressors and you can always derive any other format from them. MC10 supports APE natively, FLAC with plugins.
- If portability is your chief concern (ie you want to use the files on a portable player) then VBR MP3 using LAME is a good compromise between size & quality, and they files will play on just about anything. MC10 supports VBR LAME MP3s natively. (But you should re-rip) This option has been my choice, I have not regretted it, the only other option I would consider is lossless.
- If filesize is your chief concern, then WMA or OGG produce equivalent quality to MP3 at a smaller filesize. However, WMA is potentially DRM encumbered, and OGG is not really widely supported on portable devices.
Folks, correct me if I'm wrong here?
We might consider making this a sticky - it is a question that has been asked many times before.