From a Facebook conversation with Lexington, he said this about the new Necron models:
I want to know who the f*** decided that "hats" was the way to go with the line.
You see what he means? Hats. They have hats now. They didn't use to have hats. Check out these classic Necron Lord models:
See? Classic Lords had no hats. However, the segmented metal cloth on the new models reminded me of something, but I couldn't put my finger on it. Then, while looking at the GW website it hit me:
Of course! The old 2nd Edition Necron Lord had a silly hat too! So it seems that the new models are connecting thematically with the very old models. Plus, as Lexington said:
"I'll give that it's a hard concept to differentiate, though."
They are all skeletons. Making them look different is hard and hats are an easy way to do it that makes them look more Egyptian.
Though I have no idea what's up with the chin on the Cryptek. Is it supposed to be like an Egyptian fake beard? It's REALLY big. Check it out.