I'm willing to grant that Cinder might take skill since she was trained by a huntsman (not raised well, but at least trained, though that's another story...)and is older than Azula.
But Cinder being the stable one? That's a laugh. Yes, Azula was crashing out hard near the end of the show, but at that point everything was basically falling apart around her. Cinder has only gotten more petulant over time, whether she's winning or not, though maybe that's just a side effect of losing her aura (figuratively speaking).
That said, yeah Cinder takes the stat trinity. Even if you scale the Avatar state higher, it's hard to argue Azula comparing to that.