Earlier quoted context omitted.
They're "always" running, so they can notify you out of the blue, without you having to initiate a conversation. It's really nice UX to get a message from my assistant saying "hey, it's time to leave for the gym, and don't forget the supermarket bag because you're picking up milk on the way back, as you've run out".
Hmm, Google Gemini has access to my Google Tasks and can set reminders. It's also asked me if I want it to check something at "tomorrow 9am", and when I said yes, it managed to do that.
For me, Gemini has been hit or miss and somehow less useful than Assistant was 2+ years ago.