With regards to the AAC or the LPCM, I think that the 2 channel is more flexible is going to sound better than MP3, and it’s the standard that you usually hear coming out of most devices.
The 4 channel is going to be a higher quality, you hear it used on DVDs, sounds better on surround sound, etc.
I assume that you’d go for higher quality in the long run, but what kind of project are you shooting for?