Okay so here it is. Why websites with WWW are better than naked URLS ( those ones without WWW)
Why should I use www?
You should use www because today you have a small web site, and tomorrow you want a big web site. Really big.
The technical reasons to use www primarily apply to the largest web sites which receive millions (or more) of page views per day, web sites with a large number of services across several subdomains, and virtually any web site hosted in “the cloud” by an application service provider.
A. Performance and Speed
1. CNAME Records: Some hosting providers strongly recommend against naked domains. One reason for this is that www URLs allow the hosting provider the extra flexibility of redirecting traffic from a failing server using DNS CNAME records. Source: https://devcenter.heroku.com/articles/apex-domains
2. Cookies: Among the best practices for website developers is serving static content from a cookieless domain (often a subdomain of the website, e.g. static.domain.com). If you are using a www URL you are actually using a subdomain as your canonical domain (www.domain.com is a subdomain of domain.com) and cookies will not get sent to other subdomains (e.g. static.domain.com). If you are using a naked domain (non-www) as your canonical domain, the cookies may get sent to all your subdomains, including the subdomain used for static content). In short, a naked canonical domain can prevent one from creating a cookieless subdomain.
B. Google, Facebook, Instagram Uses The www
If you listen to a hundred “SEO” experts you’ll get a hundred different opinions. If you’re smart you’ll stop trying to learn from the “experts” and start learning from the brands that are at the top of search engines for the most valuable keywords and phrases. In the case of www vs. non-www, you can take note from the biggest and best search engines. Google, Yahoo and Bing all use the www. That should say enough by itself.
A Note About Branding
Admittedly there is no direct SEO difference in branding your site as www.domain.com or just domain.com. That said, when people see a www they immediately think website. I’m just assuming that branding your website with a www is much more effective than without it. Of course, you could always brand your website with a www even if the canonical URL is naked (I did this with my first website), but doing so may lead to more www links. Not good.
Have A Naked URL? …Don’t Go Switching Just Yet
If you’re starting a website from scratch I highly recommend starting with a www canonical domain. But what if you’re not starting from scratch? Based on the above reasons websites with a naked URL should switch to a www right?
Perhaps much worse than wrong.
If your website has already begun to gain natural links to you naked canonical URL the last thing you want to do is change your canonical URL. All those links would pass through the redirect and you would lose a portion of that precious PageRank you’ve spent so much time and effort earning. You already made the decision (whether intentional or not), and it’s time to move forward. Like me, you can always make the better choice on your next website.