If you're not an audiophile, I would say don't bother with anything more than 192kbs for mp3 and aac. If you want to be sure of compatibility with any device ever, put into mp3, otherwise, aac will give you slightly better quality and smaller file sizes.
All music from iTunes is encoded in aac, but the iTunes plus stuff is 256kbs and drm-free, while the rest is 128kbs iirc.
Obviously, if you don't care about space the files will take and value sound quality the most, Apple lossless or 320kbs mp3 will always be good.