"Proceduraly" and in 99% of cases the PICs decision will be the correct one. Regardless of the FOs experience levels.
Practically the FO should take over the aircraft any time it's obvious their life is in danger (CA continuing with fire bell going off after 1 notification of the engine being on fire followed by 2 abort calls from me, luckily in a simulator). Also, years of experience on a particular air-frame has a way of "adding" performance, particularly in smaller A/C.