I can't speak for the GP, but I lived there for a month with my wife and 3 kids. During that trip we spent extended time in Salzburg, Munich, and Vienna, and Vienna was my least favorite.

It's hard to put my finger on why I liked it less. The people weren't as friendly, ethnic diversity increases as you move further away from the city center that I think might contribute to the lack of community feeling. (Language barriers)

There's a lot of "culture", but a lot of it feels very touristy and classical, and not organic or natural to me. I don't know, the city felt a little fake and dreary to me.

It's also not as naturally beautiful as the other two (but to be fair it's hard to compete with Munich and Salzburg).