I was wondering if there have been any studies on this topic. Which one do most users prefer? For example, Wordpress separates the front-end views from the site administration views. Different theme etc. I've seen that other CMS apps, especially web apps, mix the admin with the site. The advantage is that the administrator sees the site changes he makes "live." But the interface is a little more clumsy.
In most cases one cannot integrate all administration controls with end-user view. Things which definitely must have their own view to be managed are actions and settings respecting whole site.
We can however integrate actions and settings respecting objects (eg. articles) on their end-user "read-only" view.
Generally such integration is convenient and understandable for user, either when content editing is compliant with "what you see is what you get" philosophy or when object's settings can be changed in it's context.
It is good to mention there are issues which, when wrongly handled, can undermine the supremacy of integration. End-user view tend to
- contain elements useless for administrator (like ads, social bars, some navigation bars, prompts, warnings),
- enable some actions for end-user, eg. form submit (comment, feedback form), user edit.
These, unrelated to the administration, contents and actions should be hidden, disabled or muted when seen in "admin mode" to keep it clean.
There are also actions or comparisons administrators would like to take on set of objects. This actions can be integrated with list view for end-users, but this time integration is not always possible or advisable.
- The goal of administrator list view is to compare object's attributes and to select some of them to take action, it can also involve object filtering.
- The goal of end-user list view is usually just to present and link to objects' views, involving simple navigation.
Administrator list would be seen as a condensed table of items, whereas end-user usually would like to see just bulleted list with nice presentation of objects.
Those two different goals make integration not so easy or even impossible, unless end-user would want to use the list view in similar way to administrator (database-like web app case).
Design and effort compromise
You mentioned that WordPress separates administration and end-user view. If it would be decided to move article administration controls to end-user view, that will require all WordPress themes to serve a layout for them. I am almost sure, it is just the cost and effort which it would involve that stops such decision.
Solution that is understandable, clear and convenient is always the one which users prefer. :)
Therefore in my opinion integration is preferred solution, but answer to the question to what extent we should integrate administration with end-user view depends on character of web application.