Fangraph’s Chris Mitchell recently published the latest version of his KATOH rankings. You can read all about how the rankings work here, and how they’ve been improved here. Essentially, he has a ranking system that takes into account different items based on which level the player is in, his size, and his WAR potential through 28 years old. That’s the short end of it but I recommend you read the links above if you want to know more about this system.
One of the biggest additions he’s made this year is the defensive abilities of each prospect.