A speaker's style of communication is also very important in making sure to communicate effectively. "Speaker" and "audience" are really terms that fit any situation in which one person wants to get their point across to one or more other people. But the circumstance of the communication is a primary key to its effectiveness.
For example, when you are attempting to convince your friends of something, would you use the same language and phrasing that you might, if you were stopped in your car by the police? How about in conversation with your parents? Or the admissions committee at a college you want to attend or with an employer interviewing you for a job you want? Each of these circumstances requires a different tone, which might require a completely different approach, different word choices, and a different manner.
So, the audience itself, the speaker's relation to it, and the circumstance of the communication are key elements in whether the communication will be effective or not.
A speaker has several obligations when presenting a speech to an audience. First, he must be accurate. Opinion is allowed, of course, but any factual information or use of data must be correct when one is presenting as an expert behind a podium. Second, he should speak on something which is of value to his audience. Obviously there will be those who won't listen or don't care; however, a speaker does no one any favors--including himself--if he doesn't address the audience about something they are likely to want to hear. Finally, he should be alert to the feedback of his audience and adapt as needed whenever possible. The more formal the presentation (such as, let's say, the State of the Union Address), the less likely the speaker is to change; however, being alert to the reactions of the audience (feedback) can improve the experience for both speaker and audience. To that extent, then, I say the answer is your first choice--meet the demand of the audience.