Quote Originally Posted by Gazius
I build 4's over 2's, typically, because your regional MIC can be built up to level 5, and allow for the best recruitment options from local region troops. With 2's, you need wait until either a marius or even augustus shows up. If I have a huge region conquered where all I have is 4's, I'll sometimes build a 3 for the economic benefits. Read the descripts on the government buildings, I think they have some strategy advice on their use, and it's worthwhile to weigh the benefits of each building.
The problem with building typeIV is that you get a negative happiness bonus. And most places don't have anything in local MIC 4&5.