Both QB's came in and played under less than ideal circumstances in tough games and performed well. Each is highly capable and brings a slightly different skill set to the table.
Kenny G. had the amazing comeback win against Purdue, and has the record for the longest pass play in OSU history. He was as cool as the other side of the pillow. He could run and pass, and just hardly ever made a mistake. He ran the read/option to perfection. He was the leader in the locker room, not Braxton.
Cardale is simply 3-0, with all wins in "1 and done" games including the National Championship. He's 6-5 / 250 with a cannon arm and has the unique ability to truck defensive linemen.
Hypothetically, with all things being equal (good receivers/RB's, capable Def.), who do you want as your backup and why?