It depends on your requirement. If you were to fire a page view call, you will need to go for s.t() call. Otherwise we should choose s.tl() calls for link calls (non page-view call; it doesn't count towards a page view). For example, if someone clicks on a link on your page which downloads a document, you wouldn't want to count that server call towards a page view. Another example, if someone clicks on a link on a page of your site to navigate to other sections of the site and if you would want to track the link click, s.tl() calls are the ideal scenario.