The advantage of AIFF over WAV on a mac is that it keeps the meta data safe. Otherwise they both sound the same as long as the sample rate is correct.
This is a good point and cannot be stressed enough. I would strongly encourage choosing AIFF over WAV on a Mac, based on my own experiences. You will save yourself a whole lot of hassles in the long run, especially if you ever need to restore your files, copy files, or want to add artwork to your existing files.
As far as which is superior...let your own ears be the judge. I have heard differences in file types, especially when comparing files ripped in EAC to those ripped in iTunes (the former sounded better and I could pick it out blind repeatedly). Can't explain it. Don't give a rats ass whether it's bit-for-bit identical - the two files sounded different to me, and that's what matters to me. Alas, I don't use a PC thought so I still rip to AIFF in iTunes. To determine whether you can hear any differences yourself, and if those differences mean enough to you to convert your files, I'd suggest you make your own judgments rather than relying on the ears of others. Try it on a few of your favorite files and do some listening. You might save yourself a whole lot of time converting.