Ripping with iTunes...what should I do.

I'm switching to Mac today and I'd like to know a bit more about how the file types compair when it comes to ripping CD's to my HDD.

Could somebody give me a quick breakdown...or point me to a link....that compairs sound quality to file size?

My issue is that I have an iRiver H120 with most of my files in Windows Media format...I know I could use them on the Windows player for os X but I'd rather not do that.

My question is, should I re-rip my CD's into my PowerBook using MP3 format which my iRiver can read...and...it's my understanding at least...that an iPod that I may get in the future could also use...or is the Apple format better and more drive space efficient so as to cause me to want to go ahead and rip them in the Apple format?

AAC is better quality at a smaller size but it is only compatible with iPods. 128kpbs AAC is comparable if not better sounding than 128kbps mp3 at a smaller file size.

Depending on how much music you have to rip if you are going to be using the iRiver for a while I would say just rerip in mp3