I am using Finale since 2 years and just bought Finale 2009. The integration with VSL was very easy (couple of hours to understand and try it for the first time, knowing that i am completely new to VSL), much more than what is described in the Sibelius Tutorial video where it looks like a spaceship construction.
Now all articulations, playing modes (legato, staccato, pizz) are automatically switched in Vienna ! It's really great.
Out of all the musicians I know, just 2 are using Sibelius and they are comlaining about the poor quality of crescendi in Sibelius for example. This feature is working pretty fine in Finale.
I would recommand Finale, but as I have never been working with Sibelius, this is a subjective point of view...