Pro Uses an approved WC3 standard - WebDriver
The WebDriver protocol is standardized by the World Wide Web Consortium which makes it easy for third-parties to get involved and contribute to Selenium. WebDriver has been the foundation of many additional automation projects besides core selenium and has become the de-facto standard for UI automation.
Pro Active & stable support
The open source community behind Selenium has a very large & engaged developer base. This ensures a stable support channel for the tool. In addition, various companies also provide support for Selenium. This active and multi-channel support provides a much more lucrative option for developers looking to implement Selenium in their workflow.