Awakening had 28 main chapters. So, sounds about right. 

http://fireemblem.wikia.com/wiki/List_of_chapters_in_Fire_Emblem:_Awakening

28 main chapters + 23 sidequests.... (even without the 25 DLC)

Radiant Dawn, 43 chapters : http://fireemblem.wikia.com/wiki/List_of_chapters_in_Fire_Emblem:_Radiant_Dawn

Why would they include the paralogues in that estimate of chapters (can you link where you got it from?) 

As for Radiant Dawn, it was a $50 game. So for $60 you get 26 * 2 = 52 chapters. Sounds about right. 

Whats the difference between the two versions?

For the paralogues, it's in your own link ;) And even if they are "sidequests", they're an important part of Awakening (the Paralogues are the battles to get the children for example). And the Black Kingdom version is not supposed to have sidequests...

For the bold part : yes, it's exactly what I'm saying ! If the 26 chapters are real, then you have to buy both versions to have a full game. So they are not 2 full games, just 2 halves of one game. And 2 halves designed for 2 different audiences...

Apparently, White Kingdom is like Awakening, with side battles for grinding and simple objectives (wipe or kill the boss). Black Kingdom is (for me) a real Fire Emblem, without sidequests and with more various objectives (Defend a position, attack a position with limited time, survive for a certain amount of turns...). That's what I've read (White = Awakening, Black = older FE).

No I meant for Fire Emblem Fates, where are you getting the 26 chapter, and how do you know they are including side-quests in that description, wherever you got it? Chapter means chapter, and paralogue means paralogue. I doubt they were including the paralogues in the estimate. 

Sorry, mistake ! 28 chapters : http://nintendoeverything.com/fire-emblem-fates-is-the-longest-game-in-the-franchise-thus-far/

"The longest game in the franchise" : they are obviously talking about the entire game, with both versions (56 chapters are the longest games, 28 chapters are not).

And like I said, Black Kingdom is not supposed to have paralogues. So what, White Kingdom is so much longer than Black ?

For the differences between both versions : (http://fireemblem.wikia.com/wiki/Fire_Emblem:_Fates)

• • The Hoshido path will have a traversable map similar to Awakening, Sacred Stones, and Gaiden. The player can level up characters outside of the storyline chapters by paying a fee to initiate a Skirmish, similar to using a Reeking Box. Like Awakening, map victory conditions will mostly be either rout the enemy or defeat the boss.
  • The Nohr path will be more structured, having no external battles outside of the storyline chapters much like most previous Fire Emblem titles. Experience and funds are much more limited and more victory conditions will be present such as defending a base, breaking through the enemy lines, and turn restrictions for certain maps.

From what I've read: the first six chapters are the same for both games. That would mean that we have ((28 - 6 = 22) *2 = 44) + 6 = 50. So there are 50 main chapters. But we don't know if there is side content as well, like Awakening. It could very well be that individually each storyline is slightly bigger than Awakening's main story, but each game has half the side-quests that Awakening had. Either way, 50 main chapters for $60 (if Japanese prices transfer with exchange rate) sounds pretty good to me. 

50 main chapters sounds good, yes ! But it is for both versions, so what I'm saying is : you have to buy both version to get a full game. They're not 2 full games, just 2 parts sold separatly. And the 2 versions are designed for different audiences, so not everyone will be interested in buying and playing the full game, leaving us with one part of a game only...

Are they the same game with different play styles?