Passengers' perception of space, and seat pitch is (fascinatingly) directly linked to the size of the cabin. People will swear blind that seat pitch and personal space are reduced on narrow-body aircraft even when I know them to be identical across the various fleets: Upper-deck 747 is often perceived to be having lesser personal space than downstairs, although people prefer the upper deck believing it to be in some way more exclusive. The same is true of economy on A380.
It's a funny old world.