From the standpoint of a "feel good story", I'm rooting for Max. He's one of the most likeable guys in UFC history, a true warrior, and this would be the feather in his cap; dethroning the current, undefeated champ, becoming one of the few titleholders to win back a belt he lost over 5 years ago.
From a competitive standpoint, I'm interested to see what Illia has to offer. There's certainly more fights for him at FW than Max, who's basically cleared out the division (sans Volk). I hate Topuria as a person, but he's an amazing fighter and I can envision some great battles across multiple divisions, if he proves himself to be a great.
Overall though... I want Max. I just like him.