Why is Julia ranked higher than sonya ?

I swear Julia is the only reason I lose units in Arena at this point. I do run Fae as my tank, so that is a major reason why. The thing is she is a pain in the ass to deal with if you're using Meta teams, as she wipes the floor with every green (if you give her green tomebreaker) and blue mage, as well as being the bane of dragons. Her extremely high res also makes it so some red mages can struggle to ORKO if you actually run one (and few do). Thus it becomes a game of picking off her teammates so you can get something in range to get her without losing a team member.

Moral of the story: she's a beastly option for a defensive mage, though Nino is better for attack. My eventual answer to her was to start running Summer Gaius.

I agree, Sonya should be as good if not better, they are both high Res mage tanks, but Sonya has higher damage potential outside of fighting Dragons.
Sonya also works amazingly well with the new Infantry Pulse

I don't have a Sonya so can't really comment on how she plays. As for Julia, she is just astoundingly good. Baits and wrecks Reinhardt,along with pretty much any other blue. A great answer for Nowi and Ninian. Can even blow a full HP Hector off the board with Draconic Aura up.

I was lucky to pull a Hector and Julia fairly early in the game and have basically never needed to summon on green after that.

Julia is a headache for any team trying to get deathless with a manakete. She also laughs at all Reinhardts, which is a super relevant niche she had over Nino (who needs neutral res and Fury 3 with a res buff to possibly live DB3 QP Moonbow Reinhardt).

JULIA VS SONYA quick analysis for you !

https://fireemblem.gamepress.gg/q-a/late-answers-sci-yan-moshi

Plus an anwser to your question "why is Sci-Yan 's Ike "very unoptimal" ? "

Hope it helps!

She is one of the reasons I don't play nowi in arena anymore. Because of Reinhardt, she is everywhere now haha