It’s a toss-up, as far as I can see.
It was the moral argument that spurred the anti-slave states to take the political actions that they did which precipitated the war, and their far superior economic might as “the Union” – because they were generally more industrialized, since they did not primarily depend on low-skilled agricultural workers – slaves – on plantations and were therefore able to project that economic advantage through all four years of the Civil War on “foreign soil”. Had they not had the overwhelming economic advantage they had, they never could have survived an expeditionary war of that duration and that length (especially given the awful leadership through much of its prosecution). Moreover, without the moral issue driving their continued participation, they may never have continued to accept such a price – in men and materiel – to the successful conclusion, but would have sued for peace and settled halfway through.