Selenium was introduced as a part of version 1.0 of Selenium. Selenium WebDriver was introduced as a part of version 2.0 of Selenium. Selenium RC is deprecated and obsolete now. Though some users still use Selenium RC, the support for it is not there anymore.
Selenium RC enabled the feature of recording scripts in multiple browsers namely Chrome, Safari, IE and so on. Also, it had communicated with the browser via the Selenium RC server.
Selenium Web Driver supported cross browser testing and did not require the Selenium Server which enhanced its speed of execution. Overall Selenium RC had an architecture which was not at all easy, however all the complexities got removed from Selenium Web Driver.
The following lists down why Selenium WebDriver is preferred over RC −
Selenium WebDriver handles page elements more efficiently rather than Selenium core.
Selenium RC has complex commands and unnecessary APIs. While Selenium WebDriver APIs are clean and simple.
Selenium RC does not work with HTMLUnit browser. While Selenium WebDriver supports HTMLUnit browser.
Selenium RC has the ability of generating HTML reports for test result generators. While Selenium Web Driver is not capable of any in built report generation.
Thus we see that Selenium Web Driver overcame most of the difficulties of RC and is the faster and more efficient version of Selenium.