Again, I'm not positive on this, but if memory serves me correct it should be right: The coupe spring will "lower" the vert more because it's softer, and due to the extra weight. The vert spring is made stiffer to support the added weight.
I can't find any specs on the MM site or on Eibach's site. Crappy tech on there.
I know the vert springs are progressive. The rears are about 165/210 and the fronts are about 285/400. The vert's ride is supposedly softer than a coupe's. If you install SFC's, the ride will change and you will want stiffer springs, otherwise you will do "hand-stands" when you brake. I installed some 1/2" Mach 1 springs (650 front, 250 rear) and I am much happier.