but it is still significant as the individual plays are far from equal
depending on your HC, you may not have the HB Flare, or not have the great Singleback normal inside running or you miss some of the best defensive plays like OLB Flat Zone or 46 Heavy 2 Deep Man Under or the Nickle Strong Formation.
There is no Coach that gets you all the great play, so it is really a very strategic decision.
And yes, it is nice that a higher rated HC will help your players reach their potential quicker, but for me the selection of playbooks >>HC rating