I'll jump in way late to say that I'm an AC9 user who's coming back to VW now that it's reached 12.
AC is not the gold standard of anything, save over-blown promises, buggy software and a prohibitively restrictive way of modeling.
Their BIM claims are outlandish, as there is no user-friendly way to get BIM information out of the program. With several days effort, you'll at most window and door schedules.
The worst part is the inability to model in 3D, at least from my perspective.
The best part of AC vs VW, IMO, is that the model is the model. In 3d you don't just see one layer occupying the same sapce as another, as in VW. But, with 12, VW has mostly fixed this problem by automatically stacking layers.
If you haven't purchased yet, ask you AC reseller to rake a wall. Make one end 1m high, and the other end 2m high. The reseller will have to place a roof over the wall, perform a boolean subtraction, and then create a layer on which to hide that roof. If he ever deletes that layer, or moves the wall, the boolean will not stick, and the wall will lose its rake. AC is full of that kind of nonsense.
I am just getting back into VW, however, and I don't really know what kind of work-arounds and pitfalls await here.
Some people are going a third route, building models in Sketchup and exporting to 2d CAD programs for drafting. This may seem like a step backard from the BIM dream, but Sketchup makes modeling so easy, you'll always want to work with it. I am just beginning to go down this path myself, using VW12 as the CAD program. We'll see where it ends.
Check out the work of Greg LaVadera for examples of SU + 2d CAD.
My advice: avoid Archicad, especially version 9, as V10 is due out in Feb/Mar. Maybe you can re-evaluate V10.