Uncommonly ambitious, but that does open the door for unique flaws.
"Hearth's Warming Eve" is perhaps the greatest example of how much more ambitious S2 often is than S1. This is an episode based solely on the lore of the fictional universe, which is something very different for MLP. It's an active effort to expand the world the show takes place in, and for that it should be commended. It's just a shame that in many ways it didn't go far enough.
First of all: Historical characters are played by the mane six. While it makes sense that they would be honoured with that after all their exploits, and it's a good indication of their fame, the simple fact is that not a single one of the mane six is stated to be a trained actor. Having these characters play the main roles in this historical play feels forced, and this is only compounded by how the historical characters are shown as being uncannily similar to the mane six. As far as coincidences go, that's quite a stretch.
The episode needs to be praised for taking a darker and more serious route, but it's still hurt by the excesses of the main six's personalities. Their similarity to the mane six again makes it seem almost like these were characters formed to fit the story instead of actual historical figures, and is a bit immersion-breaking. Moments where jokes based on the not-Mane Six's personality take focus away from the historical story come off like a safe bet to avoid making the episode too much of a risk.
Still, the story has a potent theme of its core about not being hateful. It's a different message than the usual, taking on more serious topics like racism in the form of the tribes' prejudices about each other. Perhaps the fact that the cast consists only of an unreasonable leader and a reasonable underling for each tribe undercuts it a bit, but even despite that the thematics are clear and deep. Still, it could serve to have a larger scale.
Again, it's an ambitious, risky episode. In some ways it's still a bit too safe, but it does a lot that's different from the usual that it's highly commendable. The only real thing to complain about in this episode is that it could have gone even farther, and it's disappointing that it felt the need to stick to some staples instead of building the world further. All the same, it's a very interesting episode, and one that is more daring than the norm.