What are the benefits and drawbacks of having flat foot?

No benefits.: Many drawbacks- inefficient gait, more easily tired, pain, burning, etc. More prone to bunions, hammertoes, calluses and corns.

no drawbacks either: A severely flatfoot can be a sign of many mechanical problems with the foot, but an otherwise healthy, stable and flexible, but flat foot can be pain free and function well for athletics and heavy manual labor. Several scientific studies have evaluated the relationship of flat feet to put pain and have found very little link between them.