Both have the thing that many QB experts (NFL types) say you can't be taught: accuracy. And when the great QB coaches talk about the most important attributes of a good NFL QB, accuracy comes out 1st or 2nd. After that the brains to read and process the D quickly. Both Rosen and Mayfield are said to be at the top of the class on that as well.
I suspect that Darnold will be OK; Jackson will not be a starter (his style doesn't lend itself to the NFL), and Allen will struggle due to an inconsistency and lack of accuracy that was seen throughout his college career.
Arizona got a good one. So did Cleveland.
