Two areas:
1. Does it take the HomePod mini more time or less time than the original HomePod to know that you said "Hey Siri"? This would be time from you saying Hey Siri to the acknowledgment of activation
2. Does it take the HomePod mini more or less time than the original HomePod to understand and process a request, such as "Hey Siri, set a timer for 5 minutes"