Fire Emblem: Fates is a good game

Playing through Conquest right now and have got to say the amount of improvements they have made is tremendous; there are playstayles fitting any type of person whether you want things to be easy and enjoy the story or are up for an incredible challenge this new entry in the series has got it all.

There are three modes to choose from:

Classic - Which "retires" your defeated units for good once they die in combat.
Casual - Like Awakening where your defeated units return on the next map.

and one more addition which was not in the last game...

Phoenix - Revives your troops as soon as they are defeated.

With that being included you could easily say this is the easiest Fire Emblem game yet. There is no benefit from playing Classic over the other two modes that I am aware of however the satisfaction is still there. Furthermore, this game's multiplayer features have taken a step to the next level. You can now visit other player's castles to gather resources and materials as well as battle them either on their turf or yours.

If you defeat them in their castle with No Handicap activated you will be given the choice to recruit one of their members(however they will not develop social ranks with you) or to inherit one of their skills at a discounted price. This makes multiplayer something beneficial to all players, even those who don't usually delve into those aspects of the games they play.

You can either visit by streetpassing, entering a castle address, getting a recommendation, or searching through top rated castles based on feedback left by other players.

I have yet to try out Birthright or get to Revelations. However, if you are wondering what the differences are... here they are according to what I read in-game:

Birthright: More chances for gaining EXP and Leveling up. Defend Hoshido.
Conquest: More challenging maps with better treasure but more risk. Best for those used to Classic
Fire Emblem. Defend Nohr.
Revelations: The final chapter in Fire Emblem: Fates. Meant to be played after both Birthright and Conquest.

Oh, and this goes without saying - but you will have different units based on your choices as well.

With castles you can customize, vastly different playstyles between the two choices, and a heaping helping of supportive multiplayer content - I highly recommend this game as being the most fun Fire Emblem title to date.

The only thing I can say against the game is that your character (the Avatar) will mostly speak for himself - but you will hardly be inclined to disagree with any of it. Let the clash between these two neighboring countries...  BEGIN!