The only other one I've played to any extent is the original Injustice game, which joined for the same reason: the IP it was connected to. They still have a lot of differences, namely that Injustice is really only a pseudo-game meant to advertise the bigger, badder, not-free console/PC game of the same name and genre.
In other words, my reference material is ****.
So I'll say this much: if you don't care about Fire Emblem, no reason to play the game. It's entirely built on knowledge of the series and honestly there are probably better gacha games out there. However, if you are a fan of the series, that enhances the experience. It's well-made enough that a F2P player still stands a chance in the arena. However, there really isn't a lot of PVP (though that looks like it may be changing in the next month or so). They've also been experimenting with new gameplay styles that don't rely on it being a gacha game (look no further than Tap Battles, which briefly came out for the last few weeks and may be returning soon with a new level set). Also, a bunch of Heroes you can only get by playing the game and being good at it (Bound Hero Battles), and literally can't be earned through the loot box system. Characters like Female Robin, Navarre, and Xander fall into this category. Between those, the decent but non-competitive units that are the default set, and the ready availability of currency for free players, I'll say it's a good game.