Most feel Lynn just used Roman's playbook and called plays, am sure he did more yet his connection to Rex Ryan doesn't help either. In terms of Dorsey he seems like an up and comer and fresh blood whereas Lynn has been coaching in the NFL for over 20 years. He's Dorsey's Need to Know when he came here, as we know what he's done with Josh as QB coach here already.
https://www.newyorkupstate.com/sports/g66l-2019/02/abed3b8bba2141/7-things-to-know-about-new-buffalo-bills-qbs-coach-ken-dorsey.html