There are no SEO benefits at all by choosing www or non-www, but what is important is that you stay with the one that you chose at the time of launching your website and also you can prevent redundant hostnames.
It is also a good practice to let know Google through Google Webmaster Tools which version you prefer to index.
A general advice is that for small websites you can use non-www, but for bigger websites with growing potentials www is a must.
By adding www in front of a site, it acts as a hostname that helps with flexibility with DNS, like the ability to restrict cookies when using multiple subdomains, be able to update DNS records, and more. But when you use non-WWW domains (that is referred to as naked domains) you do not have a technical flexibility.
So, at the end of the day if you want to change either setting, add this code to your .htaccess:
now-www to www for any domain:
# Redirect non-www to www
RewriteEngine on
RewriteCond %{HTTP_HOST} !^www\. [NC]
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L] www to non-www:
# Redirect www to non-www
RewriteEngine on
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
NOTE: After redirection i.e. all non-www to www, and try your pages at Google PageSpeed Insights, you will see a lower rank if you run a test without www.
More specific you will see at Optimization Suggestions, to Avoid landing page redirects.
No worries, just enter “www.” in the front of your URL to see the actual ranking.