Major advantages of Selenium webdriver over Selenium RC.

Selenium uses JavaScript to automate web pages. This lets it interact very tightly with web content, and was one of the first automation tools to support Ajax and other heavily dynamic pages. However, this also means Selenium runs inside the JavaScript sandbox. This means you need to run the Selenium-RC server to get around the same-origin policy, which can sometimes cause issues with browser setup.

WebDriver on the other hand uses native automation from each language. While this means it takes longer to support new browsers/languages, it does offer a much closer ‘feel’ to the browser. If you’re happy with WebDriver, stick with it, it’s the future. There are limitations and bugs right now, but if they’re not stopping you, go for it.

Selenium Benefits over WebDriver

• Supports many browsers and many languages, WebDriver needs native implementations for each new languagte/browser combo.
• Very mature and complete API
• Currently (Sept 2010) supports JavaScript alerts and confirms better

Benefits of WebDriver Compared to Selenium

• Native automation faster and a little less prone to error and browser configuration
• Does not Requires Selenium-RC Server to be running
• Access to headlessHTMLUnit can allow really fast tests
• Great API