For a proposal defense, focus on outlining your planned work since data doesn't exist yet. In a final dissertation defense, spend one-third recapping your original plan and two-thirds on findings, interpretation, and how it connects to existing literature.
How should I prepare my presentation? Heavy on data or heavy on the story?
Some of this is going to depend on your committee and where you are in the process. If you are defending your proposal, you do not have a lot of data. You are saying, "Here is what I am going to do." If you are defending your final dissertation, typically I think of it as maybe a third of the time reminding them what you were going to do and then the rest of the time, "Here is what I found and here is what it means. Here is how it ties into the previous literature."
