Its quite difficult to say. Sometimes the AI will only give territory maps for world maps. Thats a real pain. But it can also help you. For instance I was once playing as Russia and had only one coastal city. The Inca was the major power and was located in the S-E part of the map. I had no clue where they were until the late middle ages. If possible steer away from trading maps. Due to the continental game map it would only be of use when first contact of the other continent is made.