Most Helpful Girl
Most Helpful Guy
I think it is the person who is most afraid of 'losing' if/when the marriage ends and likely the person who earns the most or has the greater potential to earn compared to the other.
I'd wager it is more women who'd bring this up when they earn more and men less so when they (men) earn more EXCEPT when the man earns substantially more. The the man is more likely to bring up/demand a prenup more likely because he doesn't expect the marriage to last either he's been burned before or has a wandering eye for the next younger/hotter wife due to his substantial earning 'power'.
This is so simply because for men to bring up a prenup is often frowned upon though less so when the man makes substantially more. Then it is more understood that with that kind of earning 'power' they have to protect themselves.1