Although it was first to market, Siri is so awful that i hardly ever use it. But with the reorganisation to bring Core ML and Siri under the same part of the company within Apple, and with a new "chief of machine learning and AI strategy", perhaps we'll see some improvement.
https://www.theverge.com/2018/7/11/17559358/apple-new-ai-chief-john-giannandrea-siri-machine-learning
John Giannandrea is tasked with educating Apple’s assistant