On both the .46 Vnt 15 and 17 cold sides I have here, I must say they look identical. I had heard the 17 was just a re-named 15, maybe when they upgraded the shaft, and I'd believe it. The one in my truck is a .43, which is obviously different, and was from a non-VW app.
Functionally they are the same, but the shaft is necked down between the two bearing contact points on the 15, and is a constant size on the 17 and above.