Difference between the Responsive and Mobile Web Design
Mobile Web Design
Even though they serve the same purpose, these two design techniques are almost completely different.
Mobile Web Design is built as a separate entity, an addition to main (desktop) version of any given site.
In most situations Mobile Site will be powered by another platform and reside under subdomain such as http://m.example.com
Responsive Web Design (RWD)
Responsive Web Design does not require secondary site just for mobile devices. The layout will adapt to users viewing environment, whether this is desktop, or mobile phone.
What’s Better and/or Recommended
Responsive started gaining over Mobile Design last year and Responsive approach is also much cheaper and easier to maintain as well.