Design researchers have long sought to understand the mechanisms that support creative idea development. However, one of the key challenges faced by the design community is how to effectively measure the nebulous construct of creativity. The social science and engineering communities have adopted two vastly different approaches to solving this problem, both of which have been deployed throughout engineering design research. The goal of this paper was to compare and contrast these two approaches using design ratings of nearly 1000 engineering design ideas. The results of this study identify that while these two methods provide similar ratings of idea quality, there was a statistically significant negative relationship between these methods for ratings of idea novelty. In addition, the results show discrepancies in the reliability and consistency of global ratings of creativity. The results of this study guide the deployment of idea ratings in engineering design research and evidence.