It's Robertson and it'll only become clearer as their careers progress.
Rob outperformed Caufiled in the WJC on the same team, was the first 18 year old rookie to debut in the playoffs and score since Iginla decades ago, and obviously shredded goal records in the OHL that were previously held by Tavares/Kane as recent examples. The "harder league" argument holds little water considering that Rob is already playing in the NHL despite being drafted an entire round+ later.
Caufield's goal scoring is also special but he's useless defensively (look at his "controller disconnected" back check last week) and plays soft (rocked open ice last week as well, doesn't engage physically, etc.). Robertson's motor, feistiness and willingness to battle in hard areas will make him a complete scoring threat in all areas of the O-zone. Also has PK potential down the line. Just a better overall player but Caufield's draft pedigree will carry him in this comparison, for now.
They've conveniently stopped talking about Josh Brook after he fell off the map, but last year they were adamant that he was an equivalent prospect to Liljegren.
I've book marked the posts, it's a great laugh.