Regression testing between test and dev environments for 1000s or URLs?

I need to provide assurance over changes made to a site with 1000s of URLs.

What is the easiest way to do regression testing between a live and dev environment with the following structure?

 e.g.
 http://ift.tt/2f5Bk8s
 http://ift.tt/2frfr1R

Need to do visual regression testing and capture any Javascript errors in console and any 404 assets.

Is there a third party tool that will do this that can be recommended? SAAS online?