domain name question

As far as SEO is concerned is it wise to have both domain.com and www.domain.com with the secondary being 301'd to the primary desired domain?

The reason I ask is that I on purpose only added an A record for www.domain.com but wonder if it would be wise to add the domain.com one as well and just 301 it to the www.domain.com?

Comments/Thoughts?

Some users may type-in your URLs as domain.com, so it's a good idea to have it added and 301-redirected to www.domain.com.

Okay, thank you Oleg. As usual, very helpful.

Somewhat on topic: I notice cpanel servers by default add domain.com as an A record and then www.domain.com as a cname. Does this make any difference if you ant to use www.domain.com as your primary domain?

That part should be fine. Just make sure you use the two commented lines in the vBSEO .htaccess file near the top. Edit to add your domain name, and uncomment them. That will 301 redirect anyone who uses http://domain.com/ to http://www.domain.com/