It is virtually impossible for bump maps to look as good as displacement or real geometry, if for no other reason than that the edge profiles will be wrong (you will see that the shapes and shadows on the surfaces facing you don't actually affect the edge silhouette, so they're obviously faked). The effect can be subtle in some cases, and the difference then between displacement and bump mapping may be less noticeable, perhaps even hard to distinguish, but ultimately bump mapping really is a fundamentally less realistic approach. It's valuable because it's much faster to render and can work well enough in many circumstances. Like almost everything in 3D rendering, it is a consideration of trade-offs, of how much time you're willing to spend rendering, how much resources you have, and how much it will really affect the end results in your images. Those factors are unique to every scene and image, and to some degree unique to each artist as well, in terms of what trade-offs make most sense to them.
- Oshyan
