I know there is a lot of activity on that topic in this thread.: The specified item was not found.
We're prepping for an eventual upgrade and I found it very helpful.
Hi Tyler ,
As per my understanding , in addition to what you mentioned ,
Activity page is more focused on activities throughout the community , you only have the right hand side section for tiles. So if your community/space is more focused for showing the activities as user lands on the page , then activity make sense.
Overview page has option to customize the layout and also you can take off the activity at all or give activity as small share of place and can configure rest of the area with different widgets.
Hope this helps !