Answer:
The most important advantage for the Union was it's navy. The most important advantage for the CSA was it's excellent leadership. This advantage is more important then the other advantages that the confederacy had because it let the confederacy inflict high casualties and win battles while being severely outnumbered. The Union's navy was much more important then other advantages was because it let the Union set up a blockade on the CSA. CSA's excellent leadership was almost the only thing that let the CSA win battles while being completely outnumbered and outgunned. The Union's navy on the other hand destroyed CSA's economy and made time on the Union's side.