The Facebook is most active right now but use whatever you are comfortable with. The Activity Feed posts get bumped to the top by the most recent comment/reply.
Facebook has the option of sorting by most recent post to the top (chronological by post) or most recent comment/reply (bumping the post to the top). You can also turn off all notifications except this group and have email notifications for all posts for this group.?That will give you chronological order.
