That is the question. Most have made the decision at the onset, and most have controlled it through their own server side controls, but for some that are new to this decision via the Google Webmaster Console, the following site helps you decide which version is best for established sites. http://oy-oy.eu/site/www-or-not/ (not my site)
i would have thought it's personal choice. But i would 301 from one to the other to avoid any duplicate content penalties.
The tool I mentioned above is really for an established website that did not address www or non-www before. So assuming that you have some pages indexed and links coming in with both versions, the tool helps you decide which one has the most value. If you've now, late in the game, want to 301 one to the other you want to make it as smooth as possible. If your site already has 1000 links to your www version and 100 links to your non-www version, it obviously would be a lot easier to go from non-www to www. So yest its a personal choice but if you are making it after the site is already indexed and linked to you want to make the choice that is easiest from an SEO standpoint.
Really helpful, Just did that 5 minutes ago, but this tool back my decision Some green your way already. Thanks
WWW redirect coding suggestion to place in your .htaccess (if using Apache): Options +FollowSymLinks RewriteEngine on RewriteCond %{HTTP_HOST} ^DOMAIN.com [NC] RewriteRule ^(.*)$ http://www.DOMAIN.com/$1 [L,R=301]