At a minimum AIFF can support embedded album artwork whereas WAV cannot. Apple do this in iTunes for AIFF by using a RIFF chunk which contains a set of ID3 tags.
But it wouldn’t on a transcoded stream.
Would AIFF have other advantages like better handling of track length reporting (for transcoded streams)?
Not really, as the stream length is in the header, and the fundamental problem with length is that you don’t know the number of samples in the file until it’s already transcoded. 🙁
So at the time you stream the header, you have to guess. I’ve got a slot in the database that I can poke the final frame count into, and I hope to cache the “real” frame count so that the second time you play the song it will be sample-for-sample correct, but I haven’t implemented that yet.
So no, unless there are more players that play aiff than wav, it’s a wash.