Reverend Brown leads the mission with a cool head, calmness, and patience. He does not try to foist his religion on the tribe but leads by living example.
When Brown becomes ill and must leave, he is replaced by the zealous Reverend Smith. He is the total opposite of Brown, loud, pushy and believes that he is "right" and the tribe is "wrong". He has no compunction about shoving his own religious views down their throats. Anyone bold enough to go against him is thought to be a devil-worshipper.
Mr. Brown was the first missionary in Umoufia, he respected the Umoufian culture and people. Mr. Brown on the other hand did not respect the customs and promoted conflict and unrest between the Umoufians.
However, (In another paragraph) there are also various similarities between the two missionaries. Although Mr. Brown is the more "simpathetic" one with more understanding traits than Smith, its crucial not to forget that Mr.Brown's purposes to remind the reader of his real intentions. Mr.Brown, as clever as he is, still seeks a control, like all the rest of his fellow British, over the lands and societies of Africa. The comforting ways of Mr.Brown will convince the Igbos to be a part of his world, better than Mr.Smiths' methods of force and violence. If Smith and Brown make the Igbos believe in their customs, which a big part of that is religion, then they can share (take) the igbos' resources. Brown may seem more kind, but he still devishly wants the same cruel thing as Smith.