Grant was a whole lot better. His casually rate was for his worst battles was 28%. He also didn't through live away like Lee did. His battles were logical. Viksburg was fight the same day. The campain was fought at the same time.... mid may to July. That alone should put paid to the discussion of who was a better general
Grant was not a whole lot better than Lee. Grant won by overwhelming numbers and excessive force. He wasted thousands of lives on senseless frontal assaults, e.g., Vicksburg (before he decided to lay siege), Cold Harbor, and Petersburg. At Vicksburg, his "siege" succeeded partly because he bombarded civilian sectors of the city.
Grant also took credit for winning battles that others won, such as the battles around Chattanooga, where Grant either claimed credit for others' success (General Thomas's) or sought to minimize the achievements of others (General Hooker's).
Furthermore, at Cold Harbor, Grant caused hundreds of his wounded to die because he stubbornly refused to follow military protocol and call, as the losing commander, for a ceasefire to treat the wounded. Only after Lee prodded him, and only after his staff officers complained loudly, did Grant finally call for the ceasefire, but by that time most of his wounded had died. He should have been court-martialed for such disgraceful conduct.
Grant did have a noble side. He also, finally, learned not to make frontal assaults--but this was after he had squandered thousands of lives by trying them on several occasions.
Lee learned after Malvern Hill and Gettysburg that frontal assaults were usually foolish. Grant took longer to learn this lesson.