As others have stated, you'll have to choose if you prefer high market penetration or performance.
I think Away3D is great and it is a great platform to distribute 3D content/games to lots of people, but from my experience it isn't ready for a complex project such as an MMO. Sure, you can tweak stuff and go to the limits of what's possible with flash. But you're not only looking at number of triangles to be rendered here. The CPU would require quite a lot of processing power for other important tasks, such as: - Collision detection (maybe even physics) - Path-finding - Network socket handling - Entity animation and game logic These things require quite some CPU power and *will* dramatically reduce the max. number of triangles and render quality in a Flash 3D scene. Unity on the other side can use the full CPU power for game logic, since rendering is done by the GPU.
