Generally speaking it will give you better results than FG alone. It is not always faster (it’s sort of brute force). I will occasionally combine with FG so that I get the indirect lighting as well. Depends on the complexity of what I’m lighting really. Like an interior with the IBL generating outside to inside light, I still need something to fill the room.
But in VFX work, your characters are generally situated in a set. The set data usually includes and HDR of the environment. This means we can light characters with the built-in IBL for integration extremely easily.
