I'd say it's equivalent, but not a fantastic option. I think all it does is send over a different user agent for a desktop browser. On responsive web sites, I just see the same thing with the feature on as with it off. On sites that redirect based on UA, I've seen it take me to the desktop page instead.
I wish the "Request Desktop" option actually faked a typical screen size (say, 1280 x 800, 96dpi) and all the other attributes that would make a site think it's displaying on a desktop browser. It's frustrating to really want the desktop version, and have no way of doing that when the site is too "smart" for me.
I know what I'm in for (lots of zooming and panning). For some sites, it's the only way to reach certain features that the site didn't include in their mobile version.
