Meta Description
trend
70,000,000 websites

Meta Description is free to use

http://moz.com/learn/seo/meta-description

Meta descriptions are HTML attributes that provide concise explanations of the contents of web pages. Meta descriptions are commonly used on search engine result pages (SERPs) to display preview snippets for a given page.

VS

Meta format-detection
trend
2,429,851 websites

Meta format-detection is free to use

http://www.html-5.com/metatags/format-detection-meta-tag.html

When running in a browser on a mobile phone, "format-detection" meta tag determines whether or not telephone numbers in the HTML content will appear as hypertext links. The user can click a link with a telephone number to initiate a phone c...