Which is more motivating to continue a process until completion: a percentage, or the number of steps?

I’m working on a set of guides to help users learn how to use our app. We want to show which guides are available and some data with each guide indicating how far you’ve gotten. The idea is that if we show this information and constantly remind you of it, you’ll be more motivated to complete each one and learn more things about the app.

What we disagree on is how to format that information. Which is better: “You have completed 4/7 steps” vs “You have completed 57%”? Looking for data/metrics, not opinions.