This is a silly question which has fascinated PPL's, and now Flt Simers, for many years.
Actually the question should be, What are the chances of an armchair pilot landing a big jet? There must be a measurable risk of even an experienced captain getting it wrong. Read the accident records.
However, I have found myself fanticising further by trying to imagine myself on a pilotless B737 with Teropa, debating as to which of us was more likely to land successfully. Him with his huge knowledge of the aircraft systems, or me with a PPL and a 100% record of landing (hand flying) a "real" 777 simulator at Cranebrook.
I can't answer that but find either prospect terrifying. The chances of a successful outcome would not be one I would place much money on but there is probably a better chance for the passengers than if we did nothing.
To ask Teropa an earlier question in another way. If you had learned to tight rope walk with the rope about 10cm above the ground. Do you think you would be just as competent if the rope was raised to 100 metres?