There are plenty of open source solutions available for visual regression testing:
What are the main differences with using those and our service:
No set up costs. As you are going to use SaaS platform you won't need to install any software on your server. You would be able to start getting results in minutes instead of spending few hours setting things up.
Maintaining selenium browsers isn't easy. While there are plenty of hosted selenium services like Sause Labs, they all will limit your browser with memory. In case of rendering and saving large screenshots you will need plenty memory. Because of that if you host it on your own, sometimes it crashes. We have tried phantomjs, but it didn't generate accurate screenshots either.
Imagemagick doesn't handle shifts nicely. By default all tools use imagemagick for comparing screenshots. While it works fast it also doesn't handle layout shifts nicely. Imagine 2 px shift down in your header and you will get all page to be red. We have developed custom algorithm that identifies image shifts and provides more meaningful diffs.