It has been a long time since I played CIV but the reason I was happy to see SOD go away was because it felt like SOD took away some of the diversity in combat. As I remember it (And I may misremember) it was generally best to have one massive stack that would destroy everything in it's path. It often did not make a lot of sense to split your forces. I felt like I had one big Sledgehammer, and I would swing until I encountered a bigger Sledgehammer or a wall I couldn't break through. Now, I vaguely remember it being more complicated then that, as far as SOD composition, Flanking, Air power etc, but the general feel was one big Sledgehammer.
Another big difference was having Rail that would let you travel anywhere on the may with your SOD. Now I have to actually have some defensive forces instead of just relying on my SOD to be my quick reaction force anywhere on the continent.
I actually think that the SOD was more 'realistic' but the game play was not as interesting to me.
Again, I fully admit that it has been a LONG time since I played CIV, but I do remember being pretty happy w/ 1upt when I started playing CiV. Maybe it was just shiny and new at the time, but my memory of CIV was wielding a Sledgehammer