Conquest is harder. Birthright is easier. EDIT: To elaborate, Conquest has more varied objectives and there's not many opportunities to train in between chapters, similar to past Fire Emblem games. Birthright seems to mostly just be to Rout the Enemy every time and you can easily train in between chapters like Awakening and Sacred Stones. I like the characters in both routes, but some of the characters in Conquest are just incredible so far in my playthrough. Effie, a female knight, is a beast and almost OHK everything and takes next to no damage. Charlotte, a female Fighter, has an incredible skill that gives her +40 crit if the unit you're attacking is female, and considering that one of her promotion options is Berserker and also gets a native crit boost and a lot of Hoshido units are female, she'll wreck.