Percent change is the most appropriate and beneficial approach, but it does require a touch more math.
Percent change is used for comparing an old value with new values. If you are making the case for someone choosing your organization over another organization, then you are the new value. The competitor (or average or benchmark) is the old value.
The formula for percent change is:
Percent change provides insight in the amount of improvement that would have to occur for a competitor (old value) to match your performance (new value).
Percent difference is the more simple calculation that most of us can do in our head:
Using percent difference isn't wrong, but it can give a less compelling result. When working with metrics that have lower percentage, such as readmission rates, the percent change numbers can be considerably higher than percent difference.
Example: 30 Day Readmission Rates
Sometimes you would like to show how you can lower a metric, such as readmission rates. Let's say the readmission rate for your patients is 2% and a competitor's is 4%.
"You will see a 50% reduction in readmissions when using us as compared to the competitor."
"Our readmission rate is 2% lower than the competitors."
Which would you rather say? Is it time to change your approach?