"Possibly the biggest advantage was language, the jury's out on that but some scientists say Neandertals weren't effective speakers. But that isn't technology of course, only the ability to pass it along."
In comparing the Neanderthal skull with the Modern skull, it appears to me that there is an opening in the modern skull (auricular foramen?) that does not appear on the Neandertal. Perhaps a difference was the that they had a less developed sense of hearing? Hard to pass on information if everyone in your family unit is deaf.
Also, since we do not have Neanderthal soft tissues (perhaps we will find one buried in the permafrost of the tundra someday) it would seem harder to speculate on their ability to speak.
Underneath the mammoth that collapsed on him! Oh, wouldn't that be the find of the millenium!