To be honest I like the DB chapters the most, because they're the only real challenge in this game.
The enemies are tough unlike in Elincia's and Ike's party.
In part 1 the enemies are at least same level (probably even higher level) as the DB members.
In part 3 the enemies are higher level and the laguz have a massive attack power so these chapters claim good tactical play from you. You have to play very carefully. If you to play too aggressive, the laguz will tear you apart.
I really like this challenge, the best kind of difficulty for me.