Thanks for your thoughts, Philip! They’re really on point.
If you’re designing a data visualization, using the real data — as in, the data you’ll be visualizing in the live, production environment—is always the best path.
Placeholder data is useful when you don’t have access to that data; even if the data is already being collected and is accessible via an API, a designer might not have the technical know-how to get it into Sketch or Illustrator.
Think about it like designing a magazine. Using the final copy is the only way to really get the design right. But you shouldn’t wait until you have that copy to start designing; my experience is that edits are still happening the day the issue goes to the printer! The closer you can predict the final copy, the less work you’ll have to do later to fix your layouts.