Both movies are about North and South Korean soldiers who meet up at the DMZ. They are about friendship and brotherhood. Joint Security Area is a tragedy and 6/45 is a comedy.
Both movies are set at the DMZ and are a military thriller. Both have elements of tragedy and brotherhood. The difference is in the story. Escape is focused on a North Korean soldier who wants to desert to the South, whereas Joint Security Area is focused on the events that happen between a group of North and South Korean soldiers.