G Suite is the best.
I've used them in different professional settings for >10 years.
The only significant downtime that I remember was once for a couple of hours where nobody could login (if you were previously logged in or using IMAP it still worked fine, but our security settings required login confirmation every 24h so essentially all our staff was off email).
There have been other significant problems too, but they tend to happen during US office hours, so I only read about them in the tech news the day after.
I also have a legacy free G Suite for some personal accounts, Google is still letting us have those for free.
We've found that POP3 is not safe (instances of people loosing emails due to client problems), so we turned off POP3 altogether and only allowed IMAP for mobile phones.