I've been playing both Birthright and Conquest, and it's kind of sad.
Birthright is basically Awakening 2.0 in gameplay, with some rare bits of difficulty. Good castle themes, general happy tone (other than Chapter 6), but far too blatant good vs evil shit. Currently at Ch. 13. Too easy unless you make things hard for yourself.
Conquest has the gameplay everyone wanted. Stages with fun gimmicks and some definitely terrifying maps to see at first (looking at you, Ch. 10). It presents itself as being amazingly epic, with some of the best support talks from either route. That said... the writing of the main story is terrible. I'm at Ch. 21, and I'm a bit sad at how competent and cool everyone is in supports/away from the war... and then shit gets stupid again.
Haven't played Revelation, but I hear it's similar to Birthright in map structure.
Also, Azura IMO has more worth as a frontline combat unit than as a songstress. I'd give her a Heart Seal/DLC Seal ASAP.