Advantages of the North: larger population, a greater industrial base, a greater amount of wealth, an established government, enough farms to provide food for troops, land containing the country's iron, coal, copper, and gold, control of the seas, 21,000 miles of railroad tracks (allowing troops and supplies to be transported quickly wherever needed).
Advantages of the South: fighting defensively, familiar with the landscape, had generals who knew better how to fight and lead, had many former officers in the US Army with military experience (knew Union policies)
Weaknesses of the North: had to conquer a large area, invading unfamiliar territory, harder to supply Union troops as they got farther and farther from home, at the war's start about 1/3 of the Union's military officers resigned and returned to their homes in the South (lost many capable men), through much of the war Lincoln had to search for effective generals (had worse leadership than the Confederates)
Weaknesses of the South: few factories to produce weapons, few railroads to move troops and supplies, few supplies, smaller population (9 million), more than 1/3 of the population was enslaved (who often escaped and joined the Union, usually as informants or spies), poor navy