In a sustained effort to create shorter domain names, the www. prefix was dropped by those creating websites some years ago now. There really is no need for its existence, and I haven't used this prefix for years.
Non-www is definitely preferred. Shorter names in general look more aesthetic anyways. If you want to figure out how to redirect www to non-www check out [This .htaccess Redirect](https://www.siteground.com/kb/how_to_redirect_www_urls_to_nonwww/)
@Aces if you're doing this with existing pages and posts, it's best handled with a 301 redirect for SEO purposes. Not to say that this won't work in the sense of the .htaccess guide posted, but best practice.
I prefer non-www. In fact, I cringe at the old commercials where people called it "dub dub dub ya". The Ws are old school and the modern world doesn't need them to continue to function since redirects handle that end. It's also better for your print work such as letterheads, business cards, etc because you can make the name larger when you lose the www.