What is the Best Predictive Search Results Bolding Pattern?

Trying to determine the "best" bolding pattern for predictive results in the search dropdown on an e-commerce site.

Option 1: bolding the search query as the user types it in

Option 2: bolding the predictive results (everything but the user's query)

Is there a way to test which method is more effective? Or is it purely subjective?

Thanks!