A project manager is struggling to figure out the performance of the project teams in...

 According to the PMBOK Guide, one of the agile metrics that measures the quality of the team’s output is the Escaped Defect Rate, which tracks the number of problems found in the product after it has been released to the customer. The lower the defect rate, the higher the quality of the product and the customer satisfaction. Therefore, the team with the least amount of defects in their deliverables is performing better than the other teams, regardless of the number of story points they have calculated or completed. Story points are relative estimates of the size and complexity of the work, and they may vary from team to team depending on their experience, skills, and definition of done. Comparing story points across teams is not a valid way of measuring their performance, as it does not reflect the actual value delivered to the customer or the business. References:

PMBOK Guide, Sixth Edition, Chapter 6, Section 6.7.2.1

How to Measure Agile Team Performance by Wrike Guide

37 Agile Metrics — The Complete Guide for Agile Teams by Aha!