I disagree. He's barely ahead of him in the RB rankings at most places. Hall's testing and athleticism is far superior to Williams's. Will that translate into the actual game? We'll see, but if I were being speculative about things (which is all one can be with Hall) I'm going Hall even knowing what Javonte can do in the pros.
Javonte, for all his carries last year, didn't break too many when I was watching him. He had one carry he broke where he -- surprise -- got caught from behind. Now, is Javonte a valuable runner in between the tackles? Sure. That's his bread and butter. But if you're talking chunk gains and the speed to outrun guys, give me Hall again.
They're differently styled backs, that's for sure.
eta* I was also in a unique position to metaphorically put my money where my mouth was (with a little sweetener in Courtland Sutton) and did so, so I'm definitely biased.