I’ve been using a +Def/-Atk Nowi for a long time now. However, I recently pulled a four star Nowi with +Atk/-Spd IVs. Which one do I use?
How have you been using the +Def one? Baiting enemy attacks I assume?
The -spd one isn't bad if you use her the same way, as long as you really invest in that attack stat. Push it up with stuff like fierce stance and atk refine on her weapon and give whoever wants to initiate on her a really hefty counter attack. Vantage is even a good option in this case to preemptively KO.
To answer your question, yes it can work, but I don't know that it's worth switching from your existing one.
The 2nd Nowi's Atk boon isn't going to make a huge difference with a Steady/Warding breath build and the +Def is better for it if you're able to charge an Ignis.
I just think the +Atk variant is interesting because you can potentially stack attack and instakill any low res red (Ayra, Zelgius, Mia) she encounters, or if in Vantage range drop any ranged unit that doesn't have good mixed bulk because Lightning breath can target the weaker stat.
Both are enemy phase builds, but it depends on what you need Nowi to tank. Does your existing Nowi have difficulty killing on the counter? If so, that's the only reason you might want to consider the +Atk. Else if Ignis bombing is working for you, maybe merge your new one into the +Def variant.
I like Warding Breath Aether as much as the next guy, but really consider Ignis if you can get her doubled reliably or Bonfire if you can't. You will actually get a lot more kills (and a few less losses) than you will with Aether at the expense of healing up on a fresh target. Of course, it's up to you though.
You can certainly patch up the missing defense on the +Atk variant, but alternatively you can beef up the defense on the +Def one. I know the -Atk is annoying (moreso because you're using Aether), but she is much much better at warding breath +bonfire tanking across a wider range of enemies than your +atk one would be.
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