User blog comment:Mich, Michele & Kuhla/Future Units Preview/@comment-26917552-20160126050230/@comment-26917552-20160126072106

"Have different roles," please, have you seen their SBB.

Berdette's SBB

17 combo Powerful Fire attack on all foes, adds Def Ignoring effect to attack for 2 turns &  boosts Atk  and  raises normal hit count  for 3 turns

Lucina's SBB

20 combo Powerful Water attack on all foes & adds Water, Earth elements to attack and  boosts Atk  and raises  normal hit count  for 3 turns,  Def boost relative to HP for 3 turns.

To be honest, I prefer Lucina for more hits and the elements, and the artwork is way better. By the way, I usually find the SBB the most important thing in a unit because I end up using it the most. I also found Lucina's UBB to be more useful and extra skill. Leaderskill depends on what you are doing so I will not be the judge of that.