Katie is excellent but if I had to give up her or Spica I think I'd keep the tsundere.
I can vouch for this. I started up a half dozen accounts before committing to one and ended up with first pick Sybilla and have been lucky enough to pull a Sophie and a Despara since then as well as another base summon Sybilla (I shat bricks.) Technically none of those three are particularly broken by black standards but it's hard to complain about it since I'm a free player who is now basically set for life when it comes to lightning rods.