Should you buy this, or Final Fantasy Tactics: War of the Lion? Read on....
OK, histrionics aside, I will try to point out the pros and cons for both in as impartial a fashion as possible (since this is the first time I've played either game, there won't be any fanboy allegiances showing up here).
Graphics: FFT
While in battle, both games are of the Japanese big-eyeball bobble-head variety, so there isn't much distinction. On my system, though, the graphics while in battle in FFTare a bit blurry for some reason, while they are very crisp and clear for DAD. On the other hand, the crisp clear graphics for DAD are a wee bit less detailed for characters, and a little bit more cartoony. Neither difference is a deal breaker, though.
The cutscenes are handled differently as well, with slightly different results. FFT features two types of cutscenes, depending on the importance of the place in the story. For minor storytelling, it uses in-game cutscenes with the bobbleheads talking to each other in text. For major scenes at important story points, though, it cuts to lavish and sylish fully animated hand-drawn sequences (with voices). DAD on the other hand, features cardboard cutout images of the major characters, with voiceovers. So, FFT wins this one by a landslide if cutscenes are your thing.
Equipment variety: DAD
Every piece of equipment in DAD can be levelled up by "entering" the equipment with a party of adventurers and fighting through its many randomly generated dungeon levels (100 in each). Every time you manage to get through a level it causes the equipment to increase by one level. We're talking everything here: all weapons, armor, helms, magic potions, you name it, it can be levelled up. For this reason, DAD can take a loooong time to finish if you are one of those RPG-ers who love making sure you have all the best equipment. As well, while FFT has a wide assortment of stuff, it is in no way comparable to the sheer volume of modifiable equipment to be found in DAD.
Character class variety: maybe Disgaea by a nose, but it's a close call
DAD's advantage comes in the fact that whenever you kill a monster or any opponent, that opponent's class becomes available to be created as a new minion. So, that dragon boss you beat to finish a chapter becomes available as a potential ally. In this way, you can create a very diverse array of monsters. Once created, and levelled, said minion can then transmogrify into a different class if you so choose, and start at level one again, retaining many of the original abilities from before.
Now, it looks like that has FFT beat all the way, since FFT has a set number of character classes that must be levelled in sequence in order to get to the most powerful ones. However, the fact that you can combine two different sets of features in one character in FFT means that your tweaking ability is somewhat superior.
So, all in all, the fine-tuning of a character is better in FFT, but the sheer quantity of monster/minion types is superior for Disgaea. You choose.
Story: depends on if you want serious or hilarious....
FFT is the standard takes-itself-seriously RPG, with a save the realm from the evil cardinal and his minions type of story. No surprises here, and the story isn't bad, just nothing you haven't seen before.
DAD, on the other hand, takes place in hell, where the lead character is the son of the overlord, and whose dad just died, and who just found out about it after a two-year nap. About two minutes in, though, it is apparent that this is not supposed to be a serious story. For example: about a third of the way in to the story, pictures of the young prince in some sort of compromisingly embarrassing position get out (everyone who sees them reacts with something like "gee, I didn't know you were into THAT!") , and you have to track down the guy who has the negatives.
I preferred DAD's story, for the sheer novelty of it not taking place in some mystical dark-ages realm with lots of "thee"s and "thou"s.
Battle mechanics: a tie
Both feature very slick, easy-to-use interfaces and employ turn-based strategy. Neither seems better than the other to me; both have enough depth to them that they make battles interesting for most of the game.
Longevity: DAD, although FFT is still pretty long
If you want to create a party of tanks with thousands of hit points and everyone at a minimum of level 2300 (seriously, there's no levelling limit), DAD is the winner. Add in the fact that improving items requires fighting through more levels, and DAD can take a LOT longer than the 30 hours GS reports. I've been playing for 50 hours, and am only half way, and I know folks who played the original who took a year to finish.
That said, FFT can still take quite a long time to finish as well, depending on how much time you want to invest in level grinding to get to the really strong character classes.
So, both are long, but DAD is somewhat longer.
So.
Which one to get?
Well, if you want a long and involved tactical RPG with many tweakable character classes and a typical story, FFT will do you just fine.
If you want a long and involved tactical RPG with many character types to choose from and a funny story, DAD will do you just fine.
In other words, take your pick…they're both well worth the cash.