I want to use whatever will keep all or most of the song information with the file and more importantly will do large batches of files in one shot. Its worth paying a little bit for if it's gonna save me headaches and time.
It lists m4a (which is AAC) as one of the output options. Though personally I opt for MP3 over AAC given its almost universal support. Why move from one proprietary format into another?
All transcoding will result in a loss of quality - whether you notice depends on various factors such as the original quality and the transcoding software. If your original WMA files are at 128kbs there's no point changing them into 256kbs MP3 or 256kbs AAC - you won't gain anything already lost. iTunes supports AAC, MP3, WAV, AIFF etc. If you believe the hype AAC makes
slighlty smaller files when compared to MP3 for the same bitrate. If the object is to convert the files from something iTunes won't play (WMA) to something it will, I would recommend you change them to MP3 - they'll play on your Mac, a PC, an iPod, a media enabled mobile phone and probably your toaster next year....