Robin: Alpinia was my first 6 Star, and I can personally vouch that she's amazing. She brings a lot of team utility, and she's in line to get a Bloomed evolution in the relative future. Great unit, especially if you get her equipment slots. Getting my Alpinia 4 equipment slots basically made her unkillable for most enemies. (Soloing the entire 12-5 map for the first time with just her was the best feeling.)

I don't personally have Black Baccara but she seems to be one of the most popular 6 Stars. Gotta be a good reason for that. I'm sure someone would be able to tell you what she brings to a team.

Off the top of my head, Alpinia brings you Speed boosts to your squad and a huge single target life-steal, while Baccara has an AoE attack instead of Alpinia's solo-hit and squad-stat bonuses.

Also, congrats Eab! Nasturtium is a solid gal, and so is Violet. May your new Lagurus help you hop to new victories.