AACW and CoGEE are 2 totally different games.
In AACW you get more emphasis on the strategic side of the war. Resources, management of rails and supplies and limited political choices. You can of course buy new units but the whole point of the game is to achieve good positioning, naming the right commanders and, of course, winning the war.
CoGEE is more on empire management and diplomacy. You have trade, trade routes and several resources plus reforms to make to keep people happy, tax rates, mobilization etc. Your diplomacy will affect the behavior of minors and you can also play on the hex map a tactical battle which you can't do in AACW.
Both games are very good provided you play MP. In SP the deficiency of the AI are humongous and might put you off and this is especially true in AACW which is a GRAND game but so complex that it would take NASA to program a less than decent AI. With its limited funds/manpower committed, AGEOD has done a great effort with countless patches but there is no way to overcome this kind of deficiencies.
Perhaps you could take a look at WCS Forge of Freedom which is the exact copy (in concepts) though a bit simplified of CoGEE but it takes place in the civil war. A new expansion is being programmed as we speak but again this is more for tactical grognards of the hex maps. Luckily you can also simulate battles.
The dream of every CW gamer is to have the strategic depth of AACW into the ease of comprehension and management of FoF. If you could also get the real battle into the SoW engine that would be the cherry on the cake.
As far as I know this was proposed (something like what... 6 yrs ago?) but Norb refused.
