This is a silly topic, but I guess people will always like to compare things. I have heard a few songs from the upcoming album, and also some samples, and I have to say, it doesn't suit Marys voice to sing the old Tristania songs, because we are used to hear them in a certain way, with a soprano-style. The songs were written with that in mind. But on the other hand, I do like the new songs from Rubicon much more than all the songs on WoG, Ashes and Illumination. I found those songs to be a bit boring, and Vibeke was always doing the same: singing pretty with little variation.
I guess Mary cant sing the songs on WW and BtV as well as Vibeke, but I dont think that Vibeke can sing the songs on Rubicon as well as Mary, because Vibekes voice doesnt have the power and flexibility to sing like that. I think Year of the Rat would sound bloodless with Vibeke as the female vocalist. Vibekes vocal lines was 90% of the time predictable and not very interesting to listen to. Yes, it was pretty, but nothing more. I never felt anything listening to her singing.
Yes, Vibeke seemed like a diva. But thats not a good thing, I think. the die hard gothic fans will probably prefer the image of a diva though. From what I've read in interviews from the other bandmembers, Mary is contributing to songwriting and the creative process. I love the new elements in the songwriting on Rubicon, the twists and turns of the female vocal lines are suprising and quite mesmerising.
So all in all I do appreciate Vibekes contribution in the past. But I dont think Tristania would have survived in the long rund with the old and worn operatic/pretty singing-style. It is too predictable, and I think the band needed new inspiration to be able to push themselves forward and unleash their capabilities.