By outputting only one URL for the same content, you will have the following benefits:
- You have more ranking signals coming to this URL. Example: the vast majority of mobile URLs do not have inbound links from other websites as people do not link to mobiles URLs like they link to regular web-situated URLs.
- This is also less search engine crawler traffic coming to your web servers, which is especially useful for large websites. Fewer URLs to crawl reduces the bandwidth our crawlers consume.
- Less work (and potentially less cost) building, updating and maintaining a stand-alone mobile-focused website.
- By performing client browser detection (user agent, customer preferences, etc.), you can still optimize the display for the device your customers are using. This topic is presented in detail in the document Designing Web Sites for Phone Browsers; please note that this document does touch briefly on the subject of redirection to alternate URLs for mobile content, which is not the approach we recommend for best SEO results.
- Also keep in mind our guidance on cloaking. Bing recommends you avoid cloaking