AI behavior in GA or Conquest...

I wonder, is there any difference? Especially in the diplomacy department, I´ve started a Conquest campaing starting in High with the HRE in the XL mod and no nation´s willing to ally with me. Before that, I´ve played the GA HRE campaign, starting in High as well, using the vanilla version, and if I remember correctly, the AI seemed to be less reluctant making alliances there. So I wonder, is it the mod, or the campaign mode. Both are on Normal difficulty, by the way.