If you are thinking about benefits towards participating in campaigns by bearing a signature, you need to consider what the campaign sets as a minimum rank threshold. Most campaigns will require you to be a Jr. Member at least, so even if you are a copper member it does not mean you will be able to use your signature space in a campaign. You will be able to use it to place a personal text though if you wish.

Another important benefit is for newbies is to be able to post images; this is one of the main drivers for Newbies to get a copper membership.