In Dragonball Super and the movies it followed, we see two new major forms of Super Saiyan: the Super Saiyan God, which has a red aura and is achieved via a power sharing ritual among saiyans, and the Super Saiyan God Super Saiyan, which has a blue aura and is a form that saiyans who have previously become Super Saiyan Gods can become, thanks to absorbing some of the godly power.
What isn't clear, however, is if the Super Saiyan God Super Saiyan is of comparable power to the Super Saiyan God form. Which is more powerful and -- if possible to answer -- why?