Larger brain capacity than modern humans, but oddly not larger than the humans at the time. (Humanity let it self go when we won, we were also much bigger at the time on average, but all that crap like intelligence and size takes energy and being able to more efficiently use food often wins out)

Neanderthals didn't seem to have the mental abstraction abilities to form large societies though, even compared to humans at the time. And their tech, though better than what came before, was nearly stagnant for virtually their entire existence. I think they actually trace the details of human population expansion due to long distance trade goods, because the Neanderthals barely did any long distance trade and modern human ancestors did a noticeable amount, even when just roving hunter gatherers.