Pro Card-based upgrades and reinforcements add more to each match
Age of Empires III features a new and unique card-based system that allows for you to deploy additional units and resources from your Town Hall. By eliminating enemy units and buildings, you are awarded experience, which not only goes toward your City Level (allowing you to purchase more cards out-of-match), but allows you to activate a card in-game. These cards can grant you additional soldiers, increase gathering speed of Banks and Workers, or even a fort that you can deploy anywhere in the map.
Pro Wide selection of missions
Players will see many different missions ranging from rescue missions to defensive missions. What is even better is that many of these types of missions will be mixed together into one, so there is a varying structure to each making for a different feeling to each.
Con Strategy is highly lacking
Especially in multi player, AO3 rapidly becomes a game of "build a maximum army and face the enemies maximum army, then start over". There are some things to try to make the game more strategic, but nothing much. For example, terain does nothing exept determine what types of units can pass, so placing you units on higher ground does not affect there range, and forests do not decrease accuracy and vision range/detectability.