McClellan was the General that put the Union Army into shape, the problem was that he was his overcautiousness. He avoided fights and this made the Union loose opportunities. He lacked the element of leadership.
Grant, on the other side, took chances. He was an innovative and effective leader. He was able to achieve two major Union victories, he seized Vicksburg and took Atlanta. His strategy was responsible for the Confederacy defeat by 1865.
