I loved FFT when I first played it why back in the early PS era. When I learned that there was a predecessor based on the great Ogre Battle SNES game, I tried to track it down, but it was a limited release even in remakes it seems; I never found it until this version.
I understand that there's been some updates here, a bit with graphics and the skills system was added, along with some other gameplay changes. As said, I've never played the original, but somehow this game exceeded my expectations. I've been playing obsessively since I got it, and if you are at all a fan of the genre I recommend it without reservation.
Compared with FFT, there is slightly less emphasis on building the perfect unit, and more on the best army. Battle sizes can be larger (ranging from 6 to 12 units on the playes team at a time), and some classes have abilities that rely on positioning moreso than in Tactics--such as knights restricting enemy movement, thieves getting a bonus to attack from behind (well beyond what others get), certain auras that benefit nearby units, etc. But as other people have pointed out, you can't take the best abilities from different classes and merge them (much--in a couple cases like Dragoons with Rampart Aura I could use a skill learned elsewhere, but these are exceptions). I wouldn't say FFT or TO is better in terms of gameplay, but the focus changes a bit and it is refreshing.
I don't find that all the classes play the same, either--use a rogue like you would a knight and you won't have them around for long. Rogues need to dart in when the get a chance and then run back behind the knights who have the skills to stop pursuit. There are some similar classes, though.
The difficulty of this game is just right. Most of the time I'm not sure if I will win a battle--I need a stroke of luck or expenditure of precious resources to get by without anyone losing any hearts from a guy (three strikes and a unit is gone for good) or even needed to restart. Fortunately the turn order listing and chariot tarot replay makes this difficulty forgiving if you need to take an informed risk or make a mistake--I back up a turn if I didn't know an obstacle would block my spell, for instance. And any random battle can be fled without penalty.
The story is great also. Disgaea's comic story never caught my attention for a moment. Better Tactics Ogre that risks losing me in it's machinations than Disgaea's gonzo anime antics that don't make a lick of sense. I also think it is superior to FFT in that the enemies stay more or less human forces, rather than the too common demonic forces. There's demons & monsters to fight here, don't get me wrong, but the plots are driven by humans with conflicting visions and goals rather than being possessed puppets of evil forces. And while I haven't yet finished the game (chapter 4 so far), I'm already looking forward to seeing how the divergent paths will play out in subsequent play-throughs.
Finally, the cons-- The graphics are dated, obviously. Think of it as a board game rather than a video game if you need to, its worth looking past the SNES era sprites.
The menu navigation hasn't bothered me much, so I think that's over blown, though there certainly is a lot of button pushing.
And I agree that the crafting system is poor; basically it is a time sink. It would have been better to force you to choose how to add your rare components than make most parts purchasable but give a risk of failure. But the gear you can craft isn't essential so if it bugs you you can skip it.