Out of curiosity, how steep would hills have to be to need a folder that has two chain-rings like the Tern P20 (lowest gear inches 25") or the Dahon Formula S20 (37.8")?

Or as alternative, what about the few bikes that have come with a Nexus 8 or Alfine 11? Do they provide more range than a single chainring + 8-10 speeds and would be recommended for touring?