There's more than two. -the north had better equipment than the south, but the south had better men. -the north's general Meade was one of the only guys to ever stand up to Robert E. Lee, so Lee had a kind of 'pariah' effect all through the war. -advances in firearms, especially the football shaped minie ball and near the end of the war, metallic self contained cartriges (although expense limited their use). -new tactics. people started to get away from the old ways, when everyone lined up and shot each other in rows. -the solid resolve of Abraham Lincoln There's plenty more.
The north gained control of the railroad which stopped food and supplies from getting to the south. Hunger caused many to defect. They also controlled ships and communication which broke down the south, many had no idea what was happening. To answer your question the north controlled all forms of shipping supplies and they had the manufacturing states. Cotton and tobacco was not needed in war which was the main things the south had.