I'm still foggy on this one, so I'm not sure that it helps everyone. Me and another user stared at it for a while and couldn't figure it out. Although we can see some fields are different we couldn't figure out when to use an appointment, when to use a task and when to use an activity . . . they all sound so similar. And we didn't know how these 3 affected the sync to Outlook.
Sorry, I understand "log call", but not the difference in the other 3. To me, it just muddies the waters. If I have to take 15 minutes to try to explain this to users and they still don't get it, that seems a little overboard. Sometimes "simplicity" is best displayed in a single screen, not 4 screens that basically do the same thing. That leaves the user having to think about it.