As people have said, GC3 is not better than Aransu9....
.....especially if you have a slow attacking class and have bad RNG with stacks, your DPS will be underwhelming compared to A9. Sucks for me as a fire KFM.
Not sure if I'm willing to switch to wind to compensate for this. Might have to think about that...
...and if you plan to go GC path, be sure to accumulate enough celestial steel to make the jump straight to GC6-9 after the upgrade....