To some SEO questions there are no definitive answers unfortunately. Using absolute or relative URLs to interlink related site subpages is just such a question.
Many SEOs will tell you there is no difference and the main thing is to be consistent with your choice. Others (they seem to be in majority) support absolute URLs, while web developers and designers consider it stupid and irrational.
I did my best to make up the list of all possible pros and cons and leave that for you to decide:
Absolute URLs for internal interlinking:
Example: < a href="http://www.searchenginejournal.com/about-us/4070">About SEJ < /a>
Relative URLs for internal interlinking:
(First, a short definition of a relative URL)
URL whose location is specified relative to the address of the base document in which the URL resides. It provides a shorthand way to refer to files or resources that use the same protocol, domain name, or directory path as the current document. (source)
Example: < a href="/about-us/4070">About SEJ < /a>