Mentoplasty (chin implant or chin augmentation). which gives the best permanent result?

Chin surgery: Both procedures work well. If there are accompanying bite issues see an oral surgeon for more extensive jaw surgery. For minor augmentation a chin implant is a simpler surgery.

Chin : I believe a sliding genioplasty (osteotomy) gives a better and more natural looks. The lip and the chin can be manipulated as desired with osteotomy. Therefore is more permanent.