Dan is correct and the biggest reason to redirect the www to non www or non www to www is that the chance will always exist that they will be seen as two sites and by virtue of that you will split the value of the site. We see it every day when we take on new clients.  While the DA is the same on both, the PA for a home page or important other ranking page is different. One I just finished sending a proposal on has a DA of 23 for the site. The www version home page has a PA of 32 while the non www version has a PA of 21. There are four links on the non www that do not exist on the www.

So, your call, Dan is right.

Best

xenu linksleuth is the answer to your question. Good luck. Nothing better I am aware of.

No, there are too many open variables: age of pages, localization, keyword popularity, etc.

Edit: look at mozTrust of urls and domain mozTrust of various sites. This will show you that a + b is not equal to c.

hope it helps clarify.