www vs non-www

Hi!

Just bought website ranked really good for few keywords. Here is the problem: This website is build on some custom made CMS. In GWT both www and non-www versions are added and set www version as preferred. In SERP www version is displaying... and everything is OK. I did not set any redirect yet. But internal links are all to non-www version, and if I set 301 redirect to www few things will not work (basket, search bar...).
Should I 301 redirect to non-www version and set non-www version as prefered website in GWT? Or should I leave preferred website as www version and just make 301 redirect to non-www version?

Thank you for your answers!

Good question. IMO setting up a 301 redirect to non-www version and leaving the preferred domain as www will send a confused message to the search engine. Bear in mind that by chosing a preferred domain in GWT you're telling Google which one is the canonical verson of your site. That canonical version is the one that Google will try to index and every link pointing to any of the two versions will be credited to the canonical one. If the canonical one redirects to a non-canonical, you are creating a chain and you may lose some value across it.

either way is good.
Make sure you just REDIRECT and non ranked either its WWW or without WWW to sustain the rank

Non-www version has more links but if you set in GWT preferred domain google will see page as one and display the one you set. But I am not sure what will happen if I leave preferred www version and set redirect to non-www version Is there a risk if I change preferred domain my rank will drop?

i don't think there's suck a risk your basically telling google which version to show, all the links are still there so the rankings should be fine.

what ever you do you need to make sure you use the canonical tag so that the link juice is consolidated for different url formats for that page e.g. with www, without www, with html, php file extension etc.. as G see's this as separate pages to which link juice is attributed too... If you use WP then there are few plugins that does the job e.g. yoast ... For HTML its just a one line of code which tells search engines what the url for attributing ranking is e.g. <link rel="canonical" href="url" />

I always prefer non www over the www. If you show Google in Webmaster Tools which version to show, you should be fine.

I think both works fine, wouldn't they?

Thank you all! I think I will just change preferred domain to non-www and make 301 redirect to it + implement canonical url tag. The site is not WP but it's some custom CMS in php :\