Achebe chose these two completely different missionaries because it shows two completely different sides of the African perspective. Mr. Brown is caring and uses diffusion instead of destruction, where Mr. Smith is rude and uses destruction. They serve to show how rude some whites were but also some were nice. Mr. Smith is more of the stereotypical colonist (rude, takes things away, hates blacks). Mr. Brown is nicer and is not portrayed as a colonist (nice, caring, giving).