That doesn't change the tradeoff; in a Big computer that's also a galaxy any of the stars used as an instrument for gravitational computation can't provide nearly as much compute as having a planet-sized electronic computer powered by that star.
Yeah but there are other factors. Resilience for example.
A simple black hole approaches the trajectory of that planet sized-computer and plop! All that computation gets condensed to 3 single numbers and all the information is lost (that last part is a very hot topic).
For a Galaxy computer on the other hand, blackholes could be the NOT gates.
If you have the ability to position stars and black holes as gates for computation, then the same ability enables you to ensure that they are positioned so that tinier computation around these stars can happen not disrupted - the resilience is enabled by the fictitious future technology even if you don't use that gravitational complexity.
> All that computation gets condensed to 3 single numbers
> For a Galaxy computer on the other hand, blackholes could be the NOT gates.
i.e. in the worst catastrophic case the former carries more information (3 numbers) than the best case of the latter (one bit).
