Google recently made its Google Assistant available on all IOS devices as a move to make people use the Google Assistant as their default smart AI instead of Siri.
Now the same move has been played by Microsoft to make people use Cortana instead of Google Assistant as the latest update to Cortana allows every Android user to set Cortana as their default smart AI.
When using the app for the first time it will ask you to set Cortana as the default AI on your phone. To launch Cortana you will need to press the home button for a while just like what you did with Google Assistant.
As the app is still in its pre-testing stage there might be a few things that will surely irritate you and make you switch back to Google Assistant, one of these things is that you cannot use the assistant while you are holding your phone in landscape mode.
Cortana is no more different from Google Assistant or any other Assistant out there so if you are not a Microsoft fan boy then I don’t think so there is any need to download Cortana.