Well, I caught a 'sale' and picked up FOF.. when I first started it, I was disappointed, I think AGEOD wins hands down, map/graphics wise. FOF seemed antiquated, I like the music better on AGEOD as well.
But as I got into the game I found it to be very rich in content, if you do like controlling your Army's destiny by investment and technology, this game definitely has that. As other posts I've seen say, if you don't like micromanagement then this is not for you. But the game settings are very expansive, so you can turn off and on as much as you need to tailor the game to your liking.
These are two totally different games... But they both shine in their own right. I think best solution is to own both!
One area where AGEOD kicks butt though, is the Forums... This one is alive.. the FOF one is kind of Dead.. you need help through the forums, this one is a Gold Mine!.. Thanks for all the help in getting into a great game guys!