Which culture was more technologically advanced, the Sumerian or the Akkadian? How do we know this?

I would say the Sumerians the developed a lot of modern tech and ideas for the time include sail boats, astronomy, codes of law, a numerical system, advanced water systems and most importantly a written language. The akkadian in general took these innovations from the Sumerians and used them as their own. The akkadians did eventually form the 1st "empire," which lead to the extinguishing of Sumerian culture, but most or the of their technologically was taken from the sumerians. So I would say deff the Sumerians. The akkadians simply stole and/or built on Sumerian tech