The hard things to know are the intangibles each QB has. Decision-making skill and speed. Instincts, field vision, toughness, confidence, intelligence, ability to read the defense, running style, elusiveness, etc, etc.
The ability to evaluate those intangibles in a recruit without the benefit of seeing that player running your offense is what separates the elite talent evaluates from the rest. I hope Frost & Co. are as good at that as T.O. appeared to be in his prime.
In the end, I'm just glad he will have a number of options on-campus this spring at QB. The cream should rise to the top.