Google Webmaster Tools: Preferred doman setup - does it matter?

Just looking for some help on whether or not I should set up the "preferred domain" setting in Google Webmaster Central.

if so, what is better, www. or no www?

 

I'd go with the www. It doesn't really make a difference for your SEO results, per se, but most people expect the www to be there. If you want to be entirely safe about it, redirect the non-default one to the default one, whatever it is you choose.

 

I think www should be used with the domain name.

 

1-www.domainname.com
2-domainname.com ?

1 good okey
2 no. bad.