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.

It doesn't work on a lot of sites. The user agent is still mobile safari, and web devs often have bugs for that browser in a larger screen form factor. Needs a desktop user agent.