Walker was really good at setting up blocks on screen plays and maximizing yards on those plays. Williams on the other hand is better than Walker ever was at maximizing what would be 2 or 3 yard gains for most backs into 5 or 6 yard gains for him. He also has better top end speed than we ever saw from Walker. His long run against Clemson was evidence of that. Not sure we've seen a back like Williams in the open field in terms of being able to juke defenders either.
Agree that Walker is the most recent comparison though.