thank you for your answer. The two buttons don't seem to have the same functionality though: <a class="addthis_button_facebook"></a> allows me to SHARE a page on my wall, and add a description/comment to it. <a class="addthis_button_facebook_like"></a> merely allows me to LIKE a page (and indeed adds a counter to it). It does not allow me to add my own comment, and appears not as prominent at all on my FB timeline.
Is there a way to combine both functionalities? i.e. a button that allows me to SHARE a page, WITH a counter of the # of shares next to it?