I would much prefer hardware vendor supplied drivers since they have an active interest in adding support for newer versions of graphics apis. OS vendors have proven to have a very poor track record supporting newer versions of graphics apis that they did not create themselves. (Microsoft support for OpenGL on Windows and OpenGL/Vulkan support on Mac). Calling driver vendors "unofficial" seems a bit backwards to me.
You're leaving out the "official" counterpart- Direct3D drivers. Microsoft and hardware vendors both have an active interest in adding support for new versions there.
Microsoft has interest for pushing new versions only in new OS releases and uses that to push these new OS releases - see DirectX since 10.
GPU vendors do not care, they will give you API to their hardware for any OS version that moves their wares. That's why I would trust more GPU vendors than OS vendor.
