Below you can see the upgrades done to the N63 engine throughout the years. I would say that the first itteration of the N63 is MUCH differenent from the S63 - which shows in the reliability figures.
However, it seems that BMW has done A LOT more upgrades and improvements to the N63 to bring it closer to the S63 - which already was making a significant amount of power. Still, they are not the same, although the power output is getting closer and closer and through a simple tune (and upgrade such as the charcoal filter removal) the N63 surpasses it as it's become a very capable engine.
As you can see, in the latest M50i engine, they have started using some S63 components.
"63TU3 forged rods are carried over from the 591 horsepower S63TU4. Larger turbochargers are responsible for the significant increase in power and torque. Finally, the ignition system is updated to support the new found power."
https://bmwtuning.co/bmw-n63-vs-n63t...tu2-vs-n63tu3/