For years I've used iTunes' "Create AAC version" .mp3 to .m4a feature in the advanced menu, primarily to reduce the file size of my many thousand mp3 songs. Since the latest update to iTunes, whenever I do this now, the AAC version file size created by iTunes get larger, and makes the .m4a significantly bigger than an .mp3. I understood the very point of an AAC/.m4a was to be a smaller sized file of an equivilent .mp3 while keeping a similar quality. I know large artwork affects the file size, but this still happens regardless of artwork. Does anyone know what's changed re this feature in this latest update?