Hello, If a site has all links with lower letters, e.g. www. site.com/link and somebdoy links to it with upper letters , e.g. www. site.com/Link will be any disadvantage ?
Case in URL doesn't have any impact. They both are same. Same in Google Search. It doesn't have any difference.
To be clear: case does matter after the domain name but I don't know what search engines do with two URIs with the same name. iow: http://example.com/Mysite is not the same as http://example.com/mysite to browsers or web apps.
Case in point, I had to alter my webconfig file to change urls to all lower case because people were linking to my site using upper cas letters, and Google was viewing it a duplicate content in webmaster tools.
Depends on your server settings. If www.site.com/link 301 redirects to www.site.com/Link or vice versa, you will not experience any PR leak or penalty for duplicate content.