Hello,
From an SEO perspective, it doesn't make a difference if you use either version of WWW or Non WWW.
However, you should know that only one version should be indexed according to your personal preference. If both versions are indexed, Google will consider it as a duplicate content, which will harm you website for sure assuming that no auto redirection (301 redirects) is happening between both versions.
Personally, I prefer the shorter version of course. Wordpresss for example is pushing the shorter version of their permalinks, that should tell you something.
Regards,