Google Apps FTW
1. GA doesn't require updates
2. GA supports two-factor authentication if you want to get rigorous about security
3. GA can be managed by less technical people
4. GA works fine for even pretty mediocre Internet connections - although you'll want to use a client like Thunderbird or Outlook (or Apple Mail) if the connection is consistently bad.
One nice thing about Google is they have cache servers in East Africa. Office 365 does not. Exchange would be on-premises I presume but that's a major maintenance problem.
-Adam