6.
I perfectly understand that Darth Vader became more powerful and more technically masterful of his saber. He does not however carry over the blindingly fast and utterly savage technique that Anakin and to a greater degree Knightfall Vader weilded.
That offense is only replicated by Sidious, Yoda and arguably Mace Windu when amped before his death. It is not something you see anybody but the aforementioned displayed. I give it to Knightfall Vader because he has that overwhelming offense that Vader had to drop after becoming the man in the black.
Yes his older incarnations are more powerful and masterful, but Vader only gained that in exchange for being next to Yoda and Sidious in saber offense.
I didn't disagree with Rebels Vader being more powerful in the Force and more technivally masterful with a lightsaber. Infact I said exactly that was true.
Simply put all the accolades in the world don't counter the fact that Anakin's feat of completely demolishing Dooku and Knightfall Vader's feat of almost defeating Kenobi are both better feats than any victory suit Vader has had.
Vader on Mustafar had goe days without any rest, food or water and was emotionally wrecked; then Padme and Kenobi come along and, in his eyes, turn on him, making him mentally unstable as well. Despite all of that Vader was still on-top against his own master Kenobi whom has defeated Maul, Ventress and Grievous.
A knightfall Vader with all of his mental, physical and emotional faculties in order is, in my opinion, simply more overpowering than the much more conservative Vader.