Namecoin does not hide server location, Tor .onion service does.
Namecoin does not hide visitor location, Tor does.
Namecoin needs separate DNS configuration, Tor .onion addresses works ouf-of-box, at least for Tor bundle.
Namecoin needs constant mining, Tor does not need.
Namecoin is secure from takeover, Tor .onion addresses also are secure.
Namecoin is interesting experiment and proof-of-concept, but there are better solutions. .onion FTW!
Have you ever tried to access or implement a high-bandwidth site as a Tor hidden service? Many times a site will be legal and free from interference in most of the world, but you need something like Namecoin to make it universally accessible.