From an informational perspective Bitcoin is identical to gold. Now this is purely from an information theory perspective. If the shit hits the fan and multiple EMPs pepper the globe then of course gold is the best.....
Not really provable.
I rather imagine that an EMP would result in a lot of people who now sit on their fat asses in offices being out doing actual useful work, such as moving loads of grain to cities. And there'd be massive work to do, going out and testing and repairing all the computer based equipment, as well as fast building plants to produce large transformers.
Those challenges would be met, not by governments but by the people. Chance is they'd use whatever currency was handy.
the failure of fiat money is mathematically CERTAIN! It is just a matter of when. What pisses me off is that the schemes originators knew full well that it was destinned to fail. But they couldn't giva a f*ck because they would not be holding the shitty end of the stick!
I say the new money should be the shrunken heads of bankers!
Mathematically certain? Not really, what happens is a substitute currency is put into use by the people. Over time it becomes accepted that money X is rather better than money Y, and the point is reached where the new "good money" is even accepted by governments, like for traffic tickets. At that point the old currency is doomed, but usually there are efforts to prolong it's death such as by forcing the people to exchange the "Bolivar" for the new improved "Bolivar Fuerte".
What that substitute currency might be is the question. In many countries and places, it has been the US dollar. Certainly it could be another fiat currency, or group of them. It might be something the UN tries to promulgate. It might be that several currencies coexist forever.