If the user also has M-Files Desktop installed, there is an option to open the file using the desktop Office (but not as the default operation I think). This is because Microsoft APIs don't allow web applications to access desktop Office apps directly. That option/link is a way to open the document using the M-Files Desktop client as a "middleman". So, in order for that option to work, users always need to have desktop client installed.
Using Office for the Web with the web client provides the smoothest user experience and doesn't require additional installations on the user computer.
If the user also has M-Files Desktop installed, there is an option to open the file using the desktop Office (but not as the default operation I think). This is because Microsoft APIs don't allow web applications to access desktop Office apps directly. That option/link is a way to open the document using the M-Files Desktop client as a "middleman". So, in order for that option to work, users always need to have desktop client installed.
Using Office for the Web with the web client provides the smoothest user experience and doesn't require additional installations on the user computer.