Well using PolyVox will be more complex than just raising or lowering the mesh, so I guess it depends whether that is sufficient for your needs. It will probably look ok the first time a missile hits a horizontal surface, but it might look strange after multiple explosions occur in the same area. Also if you have a hill side or cliff it might look odd. Generally you would expect the hole to go into the surface (which ever way it is pointing) rather than going straight down.
On the plus side, just using a mesh will probably allow you to have higher resolution maps. I'm intending to use 512x512 for our game, and although I will try to push it further I can't guarantee that yet.
You should also think carefully about how materials and textures will work - just using the height to choose one won't be sufficient. For example, an explosion at the top of a hill should reveal some kind of rock/earth texture, even though it is still high up. There's probably a bunch of ways you can overcome this though.
Depending on your time scale, you might want to wait and see what I come up with for my own project. I could give you a preview of the tech in a month or so.
mickey wrote:
By the way, I just thought of, if something destructs using your technology, the debris should fly around/chip off and seen by the users no?
Agreed, but the same applies if you are just raising/lowering the mesh. In both cases you would just spawn small pieces of debris along with the smoke and fireball as you modify the terrain.