Just for clarification:
The VBS series is made by Bohemia Interactive, a subset now known as Bohemia Interactive Simulations (BISim).
Within BI we share developers, models, source code etc etc between the game side and the simulation side. As I just posted elsewhere, elements of VBS2 are going to appear in the upcoming Operation Arrowhead - tracers, soldier drag and thermal imaging, to name a few.
The VBS models are generally of lower quality than in the games, but there are more of them. In addition VBS2 uses the older Armed Assault game engine, while the ArmA2 engine is much more advanced from a graphics perspective.