Mounting light on cedar siding
The method shown in the This Old Hose picture fairly involved, you're basically letting a flat area into the siding, then letting an electrical box into that flat.  It has to be done just right, especially if it's added on after the siding is finished.  It allows you to use matching cedar or other aesthetically pleasing material for the flat.  

The Arlington box is simple and easy to use, it installs without really disturbing the siding, less chance for a mistake or failure that will cause a leak, and fully code compliant when installed properly.  I don't think you could call it inferior in any way.