Basically there is absolutely no difference between www or non www version of your domain when it comes to ranking your website on search engines. Both works the same way. It's only about preference if you want to keep www or not. That's your decision.
Google gives no importance on whether you are using www or non-www version of your url. In fact Google gives more importance on the contents of your webpage and it's backlink profile. However I would suggest to choose any one of these versions and redirect the other one to your chosen version. Otherwise if same content can be accessed on different urls, it will create duplicate content issues for your website. This will hurt your ranking as well.
Google sees both versions as completely different url. So when same content is available on both versions of url, you will face duplicate content issues on your website. This is not good for SEO. The solution is simply redirecting one version to the other one. Usually I prefer non-www version only for my sites.
Since both type of urls are same for SEO, it doesn't matter which one you choose. Non-www versions look clean to me. I don't think nowadays there is any need to add www before every domain. However it's all about preferences.