i have 3 on the list, but tbh the 3 i have are all different enough to stand out quite well on there own
AGEOD Civil War II
Brother against Brother
Grigsby War Between the States
with Brother against Brother being the newest, but that also doesn't make it the best, so it depends on what your really after, control wise imo
as while the 2 others are more overall war and doesn't let you into a given battle as such, where Brother against Brother is limited to just a few battles so not the overall war period, so it's hard to say which one is better or worse or even more fun, without first knowing what your after with a given purchase regarding scale? and command and control, as 2 of them have plenty of it, and again Brother against Brother has very limited control, so kind of they may do as they like as often as the do as you ask, if the commands feels something else is better, he goes for it, no matter what you ask or do as a kind of extra fog of war addon.
so do some research on all 4 and see what takes you fancy, as imo all 3 i have are great in there own rights, as you like the period, any wouldn't be a poor choice imo