Ass. You see plenty of chicks with bad implants, stretched out boobs, veins all over the place, rock hard, looking ready to burst. Just gross. However, I have never once in my life seen an "ass implant" that looks horribly awry. Probably because I don't think they even exist.

Either way, the ass on a hot chick either looks good or it doesn't exist at all. The hooters on a hot chick can look nice, nonexistant or repugnant. The logic seems pretty obvious to me.