We can always recommend the best option for your project. All styles require editing to a different degree, very much depending on the type of object and the desired effect.
No Shadows
Completely clean background. A clean background may help with collages open the possibilities for further editing. Very limited sense of size, object are floating. Standard editing.
Natural Shadows
This is usually a shadow with a very small footprint, naturally produced with studio lighting, but reduced. These are in part occlusion shadows or contact shadows. Requires editing.
Simulated Simple
A simple cast shadow effect. Requires editing.
Simulated Complex
A hand made, natural looking shadow. Extensive editing.