When to use a Webform vs. simply utilizing the Add Content page
I think Webforms is usually more appropriate when the entered data is intended to be used by the organization behind the website and never shown to the public. 

Webforms is also useful to send the entered data by email to who should receive it. You could also do this with a content type but you would require some kind of Workflow or trigger and action which might end up being "heavier" to the server 

If you intend visitors / end users  (authenticated or not)  to see the data entered by others users then you just make a content type and use the add content form.