In regular rendering, Final Gathering precomputes Final Gather points based on the current view of the camera to achieve good quality for the particular view you are rendering.
This global precomputation step does not happen during baking. Instead, Final Gather points are precomputed for each texture that is being baked.
By comparison, the precomputation process used during baking is slower than the global precomputation process during regular rendering because Final Gather points are also precomputed on geometry that is otherwise invisible from the current camera.
The quality of the precomputation step is controlled by the attributes Final Gather Quality and Final Gather Reflect which can be found in the Texture Bake Set node. In addition, you can also tweak the Final Gathering attributes in the Render Settings: mental ray tabs, Indirect Lighting tab. In particular, you may need to tune Accuracy and Point Interpolation, while Point Density has no effect on baking.
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