It will depend on your work environment. If you office uses a lot of Outlook and heavy on Office application, I would recommend Office 365. It is USD 12.5 per use per month and that cover emails and licences for Office 2013 for each user for 5 computer (office and home). Offer 50 GB of mailboxes and 25 MB maximum send-able mail size. Not sure how much Google Apps offer.
And for those using GoDadday, setup is easy as they have integrated this with Office 365. I know Google Apps does this as well including support for other registrars such as eNom.
In terms of user interface, Office 365 is way ahead of Google if you are used to Outlook. You can also access Office Web Apps.
For organizations with Active Directory, Office 365 neatly integrates with AD and you can use AD to manage your users and the email accounts.
SharePoint has pretty new features for collaboration, including SkyDrive Pro with 25 GB of cloud storage per user. You can do simple workflow systems in SharePoint.
Lync for meetings and remote support is great. It is like Skype for Business and support multiple-way video conferencing, archiving of audio.video meetings as well a remote desktop support (you can take over a users desktop and perform 'TeamViewing'.
Microsoft currently does not have servers in Africa, closest are in Europe, so Google Apps may come ahead there in terms of latency/speed though I wonder whether server in Kenya just cache YouTube or they cache everything. You experience will vary.
Exchange Server I would rather not touch. Too much administrative headache and issues as the mail files grow.
For now, I vote Office 365.