Pros

• The primary advantage of deferred rendering is that the lighting is only computed for fragments that are visible.  Consider a scene with many lights:
• In forward rendering, each fragment requires a loop over all light sources and for each, an evaluation of the reflectance model.
• For many fragments, the lighting is computed, only to find that the fragment is not visible due to occlusion.
• In this case it’s better to only computing lighting for visible fragments.
• Deferred rendering provides better scalability as the number of light sources increases. 

Cons

• The primary disadvantage of deferred rendering is the additional storage for the g-buffer.  Everything used in lighting must be stored there.
• This becomes a difficulty when different materials are required for different objects in the scene.