From an SEO perspective neither is "better"... Either one is equally as good as the other. Your choice should be based on what you think your users will perceive more positively... You just need to pick one or the other and enforce it across your site with 301 redirects. You should also reflect your preference by setting the "Preferred Domain" setting at Dashboard -> Settings in Google's Webmaster Tools. For example, if you pick the www version as your preferred or "canonical" version of your URLs then you should 301 redirect all page requests for non-www URLs on your site to the equivalent www version of the URL (and visa versa if you prefer the non-www). This prevents duplicate content issues and split link juice / split page rank issues that result from allowing the pages to be referenced and indexed both ways.
Neither of the two is "ideal" from the SEO point of view as Canonical said. Just stick to one, build links to it, and redirect the other version to the one of your choice.
Stick to one and keep building backlinks on that. Never get confused. Decide on any of the one. You can do that setting by login to webmaster tool - dashboard - preferred domain.
what matters is that you are consistent. From an SEO perspective pick the one that you believe people will use when linking to you. I believe most people will chose "www" in the links back to your site. So I go with the "www".
No... But test.com would get credit for all inbound links to www.test.com. The redirect itself is NOT considered a backlink, merely a way of passing on credit for the backlinks that already exist to the redirected URL. Google and the other engines rank URLs. Every unique URL is considered by the search engines to be a different 'page' in their index. Most sites out there not professionally SEO'd have canonical issues because they are not aware of this fact. Every 'page' on your site should have one and ONLY one URL. This is called the canonical URL or preferred URL. For example, http://example.com http://example.com/ http://example.com/index.html http://www.example.com http://www.example.com/ http://www.example.com/index.html might all be URLs for your home page. Google and the other engines see these as 6 different 'pages' because each has a different URL. This leads to a couple of problems - 1) duplicate content and 2) split page rank/link juice. It leads to duplicate content because your site serves up the exact same content (your home page) under all 6 URLs. So one of the 6 (you have no way of knowing which) gets flagged as the original version of the content and the other 5 get flagged as duplicate. For the 5 duplicate versions of the home page, all ranking factors that are based on the content of the page are devalued in the ranking algorithm. Since Google sees them as 6 different pages, if they each have 10 inbound links from 10 different sites then what you have is 6 URLs with 10 inbound links each. The way to fix this is to decide on some rules of how to determine which URL is the canonical or preferred URL. This usually means making decisions like: - www vs non-www - show trailing '/' when referencing folders w/ default documents or hide the trailing '/' - show default document filename when referencing folders w/ default documents or hide the default document name It doesn't matter which rules you decide on for constructing canonical URLs as long as you pick one and enforce it across your site w/ 301 redirects. I always choose www, show trailing '/', and hide default document name. So my preferred canonical URL in the above example would be http://www.example.com/ but that is just my prefence. To fix the canonical issues you simply redirect all other non-canonical URLs to the canonical URL making like: http://example.com --> 301 redirect --> http://www.example.com/ http://example.com/ --> 301 redirect --> http://www.example.com/ http://example.com/index.html --> 301 redirect --> http://www.example.com/ http://www.example.com --> 301 redirect --> http://www.example.com/ http://www.example.com/ Canonical URL No Redirect Required http://www.example.com/index.html --> 301 redirect --> http://www.example.com/ Now Google will give your canonical URL credit for all inbound links to the other 5 URLs as well as giving it credit for the link text used to link to the other 5 non-canonical URLs. This means the PR will be passed from the other 5 URLs to the canonical. The redirects also cause the other 5 URLs to drop out of the index. So now Google sees your home page http://www.example.com/ as a single URL with 60 inbound links instead of 6 different URLs with 10 links each. This eliminates duplicate content issues on your site and split page rank. Your home page will gain some PR and hopefully because of the additional links w/ relevant link text it will rank better for the terms other sites are using in the links.
simply do work for both.. but prefer single at first time... and if you are redirecting then only do work for single.
Well if you had a long URL it would be better if you make it without "www" to make it shorter in the search engine listing.
Check also this post about URL Canonicalization by Matt Cutts: http://www.mattcutts.com/blog/seo-advice-url-canonicalization/