You are the networking expert for a large company

You are the networking expert for a large company. First, your company has one small branch office that is connected to an Internet Service Provider via one router. This branch office is not expected to grow or change in the next three years. Second, your company has a larger office building with three routers to interconnect within the building and also to connect to an Internet Service Provider. This larger office building is not expected to change in the next three years. Finally, your company has a campus of buildings for its main headquarters. You have a rapidly changing and growing network at this headquarters as buildings are added, departments relocated, and routers are added.
Your semi-technical boss says, "I hear about static, default, and dynamic routing, but it sounds confusing. Let's just make everything the same and use dynamic routing everywhere. I hear that is the easiest." You would like more flexibility and efficiency as you connect your networks. Tell your boss why it might be best to use different routing choices at the different locations.
Summarize your recommendations in a snappy, one page memo. Your boss isn't too technical, so keep it fairly simple to understand, but be sure to state your case that different routing choices at the different locations is the best way to proceed.