Responsive web design is all the rage now and with good reason. Adopting a responsive web design approach to create a website allows it to provide optimum user experience across any device.
This means that if you have a responsive website, it will automatically adapt to the screen size and the device that it is being viewed on to provide easy navigation and reading while minimizing the need to scroll, re-size and zoom.
Responsive web design improves SEO efforts
By having one website for all devices, you are ensuring that the website is indexed and crawled properly by search engines and that there is no confusion that can often stem from having multiple websites.
All inbound links will point to only one version of your website and your website will have one consistent URL making the job of search bots much easier. This will help improve your link building efforts and will help focus the efforts on one website and this is always good for SEO.