Definitely not the Noldor Longsword. I personally favor the Strange Ebony Sabre for that extra damage and speed. However, it's not available for your CKO by default, you have to unlock it from Burilgi the Usurper, so take that into consideration. If you don't plan to waste a Qualis Gem for his other unlocks either, then the Ebony Long Sword is the way to go, without any question.