I'd say the AI in MGE are more unfriendly, not necessarily more aggressive. You can be on very good terms with the AI one turn and the next turn they hate you. Scenarios can be tweaked to make the AI relationships a bit different, but, overall, the same thing happens. They switch from loving you one turn to hating you the next.
Aggressivness is related to the type of leader the AI is using. A militaristic expansionist leader will tend to be more aggressive than other leaders.