Why Responsive Web Design
Google states that responsive web design is its recommended mobile configuration, and even goes so far as to refer to responsive web design as the industry best practice. This is because responsive design sites have one URL and the same HTML, regardless of device, which makes it easier and more efficient for Google to crawl, index, and organize content.
Futhermore, one of the most appealing aspects of responsive web design is that a responsive website can provide a great user-experience across many devices and screen sizes. This is an important characteristic, since it is impossible to anticipate all the devices and screen sizes searchers will use to access your site. A site that works well regardless of these variables will provide a better and more consistent user-experience than a separate mobile site that is designed for a specific device and screen size.
In conclusion, responsive web design is recommended by Google, it allows one website to provide a great user-experience across many devices and screen sizes, and it also makes managing your SEO strategy easier.