Hand nailing still earns a place on repairs, detail work and tight spots. On a full tear-off and re-roof, though, the pace and consistency of a pneumatic coil nailer change the job.
A coil nailer helps hold a consistent drive depth through a long day. That can mean fewer corrections and a more even finish where repeatability matters.
Keep the hammer for the work it does best. The job gets easier when each tool has a clear role.