GhostDriver won't offer any performance gain over ChromeDriver as the only thing it is not doing is rendering the graphics on the screen which Chrome does using a graphics driver and not the CPU.
The only benefit I see is not popping up a browser window and maybe when running on a CI server.
Some stats on my test run are on my blog: http://watirmelon.com/2013/02/05/watir-webdriver-with-ghostdriver-on-osx-headless-browser-testing/