projectors vs. textures on plane with alpha channels

Hello. My question is that lets say that I have a building and I want to make its walls to have moss and cracks on it to make it look old. The texture that its using is being used by many other buildings but it is this one that I want to look old and dusty and I want something like decals as in Bootcamp demo.

One way is to use projectors that have texture for wall cracks, dust, moss etc that I want this building to have. But I can get similar results by using a plane that has a texture with alpha channel so that I can place the plane parallel and near the surface of the walls.

Which is better for performance, and more flexible in case of changes? We are developing for Android and iOS.

Thanks in advance!

Unity’s Projectors are no substitute for a real decal system (see UDK, CryEngine etc.) and are quite heavy on resources. I’d personally use planes with alpha, especially if they share the same material/texture. It’s more work for your artists (would also avoid Unity’s primitive plane as it has waaaay too many faces for this purpose) but well worth it in my opinion.