I just happened to read on a forum somewhere that absolute urls to images required more processing than relative ones. It didn't sound like the guy knew what he was taking about but it still made me wonder about this because I have thousands of virtual includes on my sites.
urls to images don't have any connection to include directives anyway, so you asked the wrong question, and in your include example both paths are relative, an absolute path includes the full url including domain name etc, but the answer is still the same, there is no difference in performance or server load