Custom hands vs Default hands for Oculus Hand Tracking

I am recently trying to work with oculus hand tracking and honestly I am feeling a bit overwhelmed and confused and so please be patient if the question I am asking is a stupid or obvious one. 

I am a bit unsure about when I might want to use custom hands instead of the default hands provided by OVRHandPrefab? I am guessing it has to do with the appearance of the hands, but is there any other reason when Custom Hands would be better to use, functionality wise?