Theres different ways too look at this, and it really depends on what you mean when you save cavity map. A lot of people mean curvature map (which has both concavity and convexity information in it) which is handy to use for various texturing effects but should NOT be throw directly on your diffuse/spec maps. A cavity map…
This comes down to the reason you don't put AO into your textures - which is that the engine should be generating the AO in realtime so that it's dynamic as part of the lighting instead of baked in. If your engine can't capture the detail that you get with a cavity map in the real-time AO, then you probably need to help it…