Slightly related, how do you like the game so far? I'm a fan of FFT and Tactics Ogre and the game looks interesting, but everything I've heard says its rough on new comers.
It's a good game. I'm not too far into it but I have no complaints about it so far. Exploding penguins certainly helps make the game better.
I haven't played any of the other games you mentioned so I can't compare it to them. The closest game I have played to it is Advance Wars which is fairly similar (I think).
It's not really comparable to Advance Wars or FFT. The Disgaea series is all about leveling up your characters to insane amounts, and it succeeds with the huge amount of depth in the ways you do that.
However, the series has gotten stale since it's pretty much the same game with each iteration. My favorite is still the first one for PS2, which I think AoD is a PSP port of.