Stone Temple tested 5 different digital assistants to see which was the smartest. The results show that Siri is the worst out of all of them. For iOS users this presents a problem as Apple has a locked-down approach, a digital prison which leaves users unable to pick and choose a digital assistant - like Android users can.

However a way round this has now been found! It's pretty simple to do. Firstly download the latest version of
Google Assistant. Open Google Assistant on your Apple Device. You will see a screen which looks like this:

Tap "Add To Siri"
Tap the record button and speak "OK Google"
That's it. Now you can call up Google Assistant by saying this phrase:
"Hey Siri, OK Google."
See, super easy! Now you can access Google Assistant on your iPhone and have a much better digital assistant experience.
Sources:
Forget Siri: Here’s how to use Google Assistant on your iPhone or iPad,
You can now talk to Google Assistant through Siri on your iPhone — here's how, Rating the Smarts of the Digital Personal Assistants in 2018