In preparation to using iTunes Match, I am trying to clean up my library of dups. If I have an AAC and a MPEG version, which should I be deleting?
Also if I added new genres such as Pop Vocal Female, is that going to cause problems when I try to match?
AAC is usually better quality than mpeg / mp3 etc..
iTunes match matches songs by Song Title & Artist, if it is a song which is available to buy on the iTunes store it will use that version in your iTunes match, which will replace any edited / added information you have put into the song tags (genre etc)... If the song is not available on iTunes It will then upload the song exactly as it appears in your current library including the personalised genre.