I was in the same boat as you two years ago mate and went for the 1.9 and haven't regretted it, think it's a great engine compared to the 2.0. As long as they're serviced regularly they're pretty close to being bullet proof. I had the same engine in a golf and it was trouble free for 7yrs. I've just actually bought a second one as I need an avant now so selling my saloon, it was remapped to about 145/150bhp and goes plenty quick enough for me and still returns 50+mpg, avant will be getting same map soon. Only downside depending how you look at it is that the B7 A4s only come with 5 speed boxes, bothered me a bit to start with but you soon get used to it.
I don't think there's many 1.9 owners in the B7 section here hence the poor response to your post but as the 1.9 was much more popular in the B6 shape it's may be worth a post over there to get a better response.