Responsive VS Dynamic Web Design

You have just decided on creating a mobile version of your website. Then comes the decision about the most convenient way of its implementation.
There are three to choose from:
mobile URL,
responsive design and
dynamic webpage.
You'll select one, which allows your users to reach target pages and perform actions with minimum efforts. The choice depends on general website structure, types of content and your audience.

A separate mobile URL is the oldest of the three. - If you require major differences between desktop and mobile versions of the website (for example, completely different content), a mobile URL is a good choice; - Your mobile website must be ranked by search engines the same as the desktop one; - If there is only a mobile version of the website, make sure that desktop users are enabled to open it; - There mustn't be chaos in redirects - mobile devices must open the mobile version, while desktops must open the full one; - When there is no corresponding mobile webpage, your mobile visitors mustn't be redirected to another, irrelevant page (for example, main page), where they cannot find the needed information or perform the needed action. Either mobile visitors should be redirected to the relevant desktop page, or there may be no redirect at all; and sending visitors to irrelevant pages perhaps would be the worst decision; - It is also widely recommended to redirect tablet users to the full desktop version of the website.

The other two types of mobile websites share the same single URL for both desktop and mobile.

Responsive design The server identifies the mobile device and its screen resolution, and the content is correspondingly scaled and presented; it can be viewed with any screen resolution, be it a mobile device or a desktop. It has no odd redirects to slow down the loading speed. The lower screen resolution is, the simpler navigation gets. Responsive design is not the best solution for heavy content, such as video - it can slow down the website.

Dynamic webpage The server identifies the mobile device and its screen resolution, and the types of shown content depends on the device. Dynamic webpage is good at delivering heavier content, and it's more difficult in implementation. Here is often used HTTP-header Vary, which prevents the mistake of displaying a desktop page on a mobile device, and vice versa; it also allows Googlebot to find mobile-optimized content faster. If you need to deliver only a part of the desktop content, dynamic webpage is what you need.

See more at: http://mobidev.biz/blog/mobile_website_mobile_url,_responsive,_or_dynamic.html