I want to convert a big number of AAC music files to mp3. The bitrates I will meet in AAC are in the range of 96,128,152,192 kbps. The available bitrates to mp3 from my converter are 96,128,152,192,256,320 kbps.
Since I know that AAC generally provides better quality at the same bitrate when compared to mp3, I need to choose the suitable mp3 bitrate for each mp3 file I will be converting. I spontaneously decided to move the quality two "steps" up for each conversion, e.g. if the AAC is 96 kbps, I move to 152 kbps MP3, if its 192, I move to 320 kbps MP3.
However I'm not sure if that's the optimal choice, since I would like to save as much space as possible by choosing the lowest mp3 bitrate necessary to avoid loss of quality.
So, what I am asking for, is someone who has good knowledge of the relative technical aspects to recommend the best choice I should make about the bitrates while converting from AAC to MP3, ideally for each one of the choices listed above.