It's taken them 150 years to conclude what the real thinkers did nearly as soon as the first Neanderthal bones were found.
Neanderthals developed more slowly than modern humans for the exact same reason that modern humans develop more slowly than apes. They have a longer adolescence which results in a superior finished product.
Bigger brains, bigger muscles and judging them from their artwork, bigger souls. Any comparison between Neanderthals and Sapiens is going to result in the study being suppressed or else reformulated to make it seem that the gulf is not as great.
Sapiens was good at breeding, killing and at spear chucking. He was also better at running on cheaper energy sources than the high quality protein that Esau required.
Neanderthals were good at everything else.