Skyfire or Gitano?

Got Skyfire from the latest banner and I was thinking of building her, but is just she an upgrade from Gitano or do they have different uses?

A little bit of both. Assuming the same level, Skyfire’s DPS is about 10% higher than Gitano’s – not counting their traits (Gitano gets at random an attack, speed, or HP boost when deployed, Skyfire makes blocked enemies take extra Arts damage ).
Their S2s give them some notable different uses though. When adjusted for the attack speed reduction, their overall DPS increase is about the same, but Skyfire adds a stun and Gitano gets a boosted range. It depends on the map which would be more useful, but it’s worth pointing out that some Annihilation 3 strategies rely on Gitano’s S2, while Skyfire is just a backup DPS.
So overall Skyfire does better damage, but Gitano has a bit more niche utility.

If you already built Gitano. I don’t recommend to build Skyfire. She doesn’t make much difference. 6* like Eyja Ifrit Mostima or even Angelina is what make thing different.