Alright, I can see why Adam has the edge when it comes to absorption. However, my vote will go to Azula.
The main reasons for this.
1. Close quarter combat is a high specialty for Azula. Avatar Book 3 during the Black Sun Arc, Azula was capable of fighting Aang, Toph, and Zuko with a hint of high level keep away without having any of her powers. She has soon lots of close quarter combat without resorting to her firebending in fights with Kyoshi Warriors, who happen to be recognized as one of the top elite fighters in Avatar verse.
2. The firebending is heavily profound in her combat. I know Adam has shields, but constant blaze will definitely be knocking down Adams shield especially when you look back to RWBY season 3 arc.
A flame torando in episode RWBY Volume 3, Chapter 5: Never Miss a Beat: was capable of completely depleating Weiss aura from 40 to 0. Flynt aura to 55 to 16. Weiss was out of commission for the battle with her aura completely at 0. This was just from a 5 second flame torando.
If a 5 second flame torando is capable of taking off 40% of aura. The existence of a Azula's fire has so much time of lasting longer than 5 seconds is not only going to burn away the aura, but will break through the Adam's shield to get to his actual health.
Flame Torando
Now imagine the precise combat of one of the elite firebenders constantly on Adam with so much AoE blaze. Adam's shield is going to fall really fast.
3. Flight is on Azula's side.
4. I can see Azula playing on Adam's arrogance if the match doesn't end to fast.