first, let me say that this is an excellent topic! however, I do not feel we can make a fair decision as to which is better. Simply put, Revan is still very much an enigma when compared to all the material about Vader. Sure, Revan is mentioned frequently, and even appeared in some books and comics. But to compare those with the utter colossus of writing that exists about Vader? Not even a fraction. Furthermore, Revan is not dead yet in the old republic story. We don't know what happened to him, only that he disappeared. Therefore, there is still much, much more he is capable of at this time. His full abilities can only be fairly judged once we have a confirmed death, one he won't be walking away from. Only then can we begin to make a reasonable comparison of vader and Revan. Only then will we have a definitive beginning and end point with which to work from. However, I will say this: in KOTOR II, Kriea tells meetra Surik that the current force users and lightsaber wielders are like children compared to the ancient sith. It is a stretch, and not one that can be confirmed by any real means, but it is possible that such a decline in mystic and martial prowess has continued well into the reign of Palpatine and Vader. I also do not feel Palpatine is the most powerful Sith Lord. He was far more powerful than nearly any force user at the time and probably more powerful than any since Bane, but I do not think he surpasses some of the older sith. He had incredible foresight and understanding of the future (one theory I`ve read is, similar to revan, Palpatine organized a takeover to build a militarily strong galaxy in preparation for a coming threat [Revan's being the true sith empire and Palpatine's the Yuuzahn Vong]). As for Vader, he gets a bit of a bad rep for the FU games. however, remember that Vader was clearly powerful enough (and scholarly enough to continue training even after falling to the DS) to live on as a "force ghost" like Obi-Wan and Yoda, as shown at the end of Episode Six. That alone is a testiment to his power. This is another reason why I feel a comprison of Vader and Revan is incomplete until Revan's confirmed death, because we can't yet know if Revan has the capacity to become a force ghost. Only time shall tell. Personally, I want to cheer for Revan, largely because of how captivating he is with his force neutrality and mysteriousness (even since the first KOTOR he's been a fascinating enigma, saying not a word, having no visible identity beyond his robes and his mask). However, I fully acknowledge Vader's great powers. it would surely be a titanic battle, one well worth watching.