Main benefit is financial. 5G plans are cheaper than NBN plans for same speed. But 5G is not everywhere.
Being in an apartment means you may not get good reception from the tower, depending on where you are in the building. The placement of the Sagemcom unit might not be convenient for your ethernet devices, and the wifi coverage might be different from existing router.
Several users have reported that Chromecast does not connect to Sagemcom wifi. And various other wifi devices. Only way around it is to use your existing router as an access point (attached to Sagemcom) to provide wifi connection.