For many (perhaps most) buildings, I imagine a simpler wheeled or tracked vehicle would be just as effective and surely cheaper, more reliable, and more robust.
Navigation for land based robots is a much harder problem. I would expect quadrotors to be more reliable actually (only four moving parts! No ground contact!) with the ability to map areas inaccessible to wheeled robots, and much faster to boot.
Why? These robots look pretty simple and have no problem going up stairs.