I don't have Rainbow Rose but I have promoted Pinkladies and Kerria. And I'm abble to clear the entire game.
I use them in that team:

It's a simple Evade team but it allow me to clear all the hardest maps (espacially Aqua Shadow EX-Destruction) with ease (I died only once on 26 runs on Pumpkin&Lantana EX-Destruction, due to bad luck on the whole mission).

Maid Cowslip is the key stone here. She gives an awesome +45% damages after 3 turns for all and a good +50% ATK after 2 turns. Just enough to cover Kerria's and Pinkladies' needs of power.
With Evade+Negate damages, it's almost impossible to die before turn 3.

Saffron add DEF buff and above all, bring Provocation to protect Kerria and Pinkladies a bit more. And she bring Magic Weakness for herself and 2 non magic girls... who are Kerria and Pinkladies.

Colchicum just gives more offensive buffs and a bit Crit. Or you can use Tritonia instead and get a pseudo second Maid Cowslip.

With that team, Kerria and Pinkladies can reach something like over 400k weakXcrit damages on Slice and Magic pests. And they are very hard to kill unless you're facing ridiculous pests with ridiculous ATK buff (like a certain Punkbee on certain harderthanhardest maps) or RNJesus decide to fuck you.


I don't have Rainbow Rose so, I can't really compare but that team is more than reliable (even if it will take some turns to become fully efficient). I think Rainbow Rose is a bit more random and can die without doing anything.

I think on Paper Rainbow Rose is a bit better but if you look at promotion cost and efficiency, both are a great choice.
(anyway, Rainbow Rose is the next on my promotion list and I think both of them are needed, at least for me and what I have).