The difference lies in the starting amount of resources, but not only.
"Expert" difficulty (160%):
- The AI player does not hire more than 5 heroes.
- The AI player does not hire new heroes if there are 18 or more heroes in total on the map (including the heroes of other players).
"Impossible" difficulty (200%):
- The AI player does not hire more than 6 heroes.
- The AI player does not hire new heroes if there are 21 or more heroes in total on the map (including the heroes of other players).
(Василь Симоненко. Люди – прекрасні)