For Jazz and Acoustics i'd give it to the 4.ai'. For other Genres the W4 performed very well especially Vocals. I still wouldn't say the 4.ai's are an improvement. But they are both great to have, when you first here the 4.ai's im sure you will be more impressed than the W4.
EDIT: Forgot to mention for the 4.ai I heard small details ticks of sounds of the music that I've never heard clearly before. The detail retrieval of the 4.ai's is very good for an IEM the details sounded better than even my HE-400.
Edited by Poetic - 8/6/13 at 2:45pm