navigation - Different look and feel between administration and end user experience?

Lets say we have an app that performs something like surveys. There are two primary types of users, administrative users who set up and build the surveys, (who are actually the customers), and the 'public' users being surved, who will also have accounts and profiles.

Here is my question. Considering how few views exist on the public end, and how different the function; is it appropriate to have a mildly different look and feel from the administrative areas? What kinds of value does this visual shift between the experiences hold?

Or should the two kinds of users get the same basic look and feel? Is there value to the two ends being visually consistent?

I caught myself preparing to go through the extra work of making a different look and feel for the public, but then realized there a good arguments on either side.