Just so you know, that is a pic of a crop, not a whip.
I don't know that there is any one 'best' material. My snake whip is made of paracord, but I've had leather (kangaroo and cow hide) whips used on me. It just depends on personal preference.
I make my own whips actually. And I always use leather when I make one. I find the material is exquisite, most people who Ive made whips for seem to enjoy the leather as well. But everyone is different. I suggest touching whatever materials you are considering to see which one feels best for you.