I am trying to figure out if it is better to advertise your site with or without the www. in front of your URL? When it says enter your URL, which is better...? http://??? or http://www.??? I know they will land on the same page, but eventually they will show backlinks. Do they get indexed differently in search engines? Does it even matter?
Generally most people type in the www. anyway (it's become more of a habit). It does not really matter because most search engines are able to handle domains without the www. and those with them (Google even allows you to choose which form you want to display). As the domain itself usually redirects to the www. anyway, they would not be indexed differently (and are rather treated as the same thing). Omitting www. is up to your choice, it depends on how you want to advertise/brand your site (e.g. wordpress.org omits "www." while Google keeps them on).
Offline I advertise with the www. because I have a .biz domain. Most people have no clue that .biz is just like .com