Even though you didn't ask me I'll throw my 2 cents in. Gurley is probably the most dynamic back with size, speed and power all in one UGA had since Herschel. Could catch, run and block.
Chubb was just a model of consistency that you could count on to break one when you needed it most. If Chubb doesn't get hurt in college this isn't even a debate, imo. What Chubb has become in the NFL has been telling on how good of a player he is. I'm biased with Chubb because of how he represented and led by example while he was at UGA. Especially through the horrific injury.
80% of people will pick Gurley because it's rare you see a talent like that at his size.