The 919 has a noisy engine, especially when cold. When I first got mine, I asked around and was told it was quite normal.
As others have said, its a very stable and forgiving bike, so the tyres may have been poor or under inflated.
The Z1000 is a hoot to ride and definately something I'd advise you to test ride before buying a 9'ner. I just didn't like its small tank, as I commute and the example I saw was corrosion ridden, only being 6 months old. Mind you, it was a press bike, so who knows who rode it where, it may have even had a trip on a beach for a photo shoot, who knows.