Not just for the "mature" violence but they could really delve into some heavy issues with the story and supports. That's why SMT IV is rated M, I think. More for the issues it decides to tackle and the general vibe of the world than just the obvious blood and guts, and strong language.
If you want a tactical RPG with a darker story, hunt this down if you can:

It's not connected to the first, so you don't need to have played that. It's also more than twice as long as the first if I remember right.
The combat system's a tad different - there's no "enemy turn", they move when you do. Makes you think much more before moving to attack something, as your target might not be there.
Lots of skill customisation, weapon choices and - get this - there are multiple endings that depend on choices you've made, and they're mostly vastly different. (I've only seen two.)
As for this whole pokemonification of Fire Emblem... yeah, not impressed. Hopefully they'll have some sort of bundle with the both of them at a slightly reduced price. (Or
greatly reduced, I'll take that too.)
How would DLC even work with this? (Because you know there'll be DLC.) Would there be two versions of DLC maps?
I DON'T LIKE WHERE THIS IS GOING, NINTENDO