I need to know if I should get a mandibular setback or a chin reduction and which one would be more effective for me? (photo)

Thank you for your pictures. If you teeth are in the appropriate position the a chin reduction via a sliding genioplasty would be beneficial  If your teeth are not in the appropriate position then a mandibular setback would be indicted.  Additionally I would recommend some submental liposuction to prevent fullness in your neck with either procedure.

All jaw procedures (mandibular repositioning) require before and after surgery orthodontics which could mean a year of braces before and several months after. A chain reduction procedure does not require braces as it does not affect the position of the teeth as the chin bone is reduced. Your excess chin would be better served by an actual chin reduction surgery

your lower jaw position would depend upon the amount of 'underbite'. When a jaw is 'setback' the teeth have to match up somewhat; so orthodontics is usually started to line up the teeth so that occurs when the surgery is done. IF your teeth are perfectly straight and line up when you look at plaster models, then surgery can be done earlier. A chin surgery does NOT give the same look as a lower jaw setback; so talk to the maxillofacial surgeon about the difference