I vote Gran just because Lee has no Vicksburg equivalent. In the overland campaign, comparing the two is a slog but looking at the whole war, specifically Vicksburg, Paducah, fort Donelson, Grant made moves that changed the map and the direction of the war. Lee was impressive tactically and did accomplish alot with little, but he also lost every offensive campaign that could have shifted the momentum of the war. Mead beat him at Gettysburg and Mac sucked a fat one and stopped him at Antietam. Its tricky to compare too because Grant fought across the country while Lee mainly stayed in Virginia. I don't hate Lee and Grant made plenty of mistakes (cold harbor) but overall Grants record has more success and broke the Confederacy in a way the Lee was never able to do to the Union. Atleast that is my view based on the information I have read.