As in conversation, there are different styles of public speaking. It is getting the balance right that is most important between them.
A conversation may be stiff and formal. Or it may be relaxed and informal. This latter condition is more effective in a public speaking situation.
A speaker who holds himself aloof, or “buttons himself up” from an audience does not communicate freely with his listeners. They feel he is holding back, not sharing his complete self. An atmosphere of restraint and reserve builds at least a partial barrier between audience and speaker. Persuasion is delayed, often it is impossible, when a speaker puts up such a barrier.
The very nature of effective persuasion necessitates a close, friendly feeling between listener and speaker. How can a listener get close to a speaker who isolates himself with extreme formality or indifference?
A style of speaking may reveal a precise manner which causes listeners to feel the speaker really despises the “common herd,” and that speaking to them is a trial for him. Any tendency to talk down to an audience or evidence that a speaker feels he is superior to other people detracts from his persuasiveness. An extremely particular person who must be sure that every hair on his head is just so-so before he speaks may cause listeners to wish
they could mess up his hair.
On the other hand, an extremely careless or sloppy person will probably not create a persuasive influence. Informality need never go to seed. But a speaker who leans in that direction probably will be more interesting, popular, and persuasive, than one whose manner dares listeners to come near him.
As with much to do with public speaking the above is only general guidance because it depends on the audience. You also need to consider what will work best in the situation and with your audience to help determine the most effective public speaking style.