One consideration for all speakers is the size of the audience. When you speak to 5 people versus 500 people, the “feel” is totally different. When you practice your speech by yourself or in front of a few friends and then go to speak in front of 300 people, you will know that there is a difference. This difference may force you to communicate your message slightly different. Every speaker has had the experience in their career of speaking in a large room capable of holding 300 people but have only 5-10 people in the room. This experience is totally different than if you were speaking to the same 5-10 people but the room was a small classroom.
The final size of your audience matters. You have to take into consideration the number of people that will be in the room and how many people will fit into the room. That is a question you must ask of your meeting planner and that answer may influence how you present.