If I have a weekly (free) meeting and I want to track attendance, is it better to use an activity or an event to do so? What are some of the pluses and minuses of each? Please define the differences.
If you use events to track your attendance, you actually get the benefit of both (since event registrations also generate activities). :-) Depending on your version of Civi (which unfortunately you didn't specify), you may be able to create your event as a recurring event. You could then import your attendance lists (assuming of course all your attendees are already in Civi; if not, then you'll need to import the contact info first, then import the participant records).
My thought is that if you go ahead and go the route of events, you're already situated to take online registrations down the road if that becomes a need, and/or to register people in advance and then send scheduled reminders. I think that going the activity route might work quite well in the short term, but prove limiting in the long run as your needs and use of Civi evolve.
Hope this helps, Lesley
The big differences in my mind are publishing and participant attributes.
An event comes with an info page, which can contain a location and map. Likewise, you can allow participants to register directly. Those are nice features, but they require setting up the text, location, registration fields, etc. An activity doesn't need any of this, but it will neither display anywhere on your site nor allow for people to add themselves.
An event also allows for details of a contact's participation in it. The participant record (which connects one contact to one event) has a status, role, and registration date along with the potential to record additional information. On an activity, a contact is the source, target, or assignee, but that's it. If you remove them from the activity, they're gone--there's no way to indicate they were supposed to join but cancelled. Similarly, there's no way to say that these people want barbeque and those people want a veggie plate. Finally, if you have more than 20 or so attendees, an activity's attendee list can get unwieldy: after a certain number of targets or assignees, CiviCRM won't let you remove people from an activity via the user interface.
There are further distinctions, but these are the big showstoppers: if you want the meetings listed on your site or you want to distinguish among attendees, you've got to use an event. Events are more complicated to set up, but with the event template and recurring event features, you can cut down on the amount of setup.