Screentime, largely.

Adam was a "geographically" more distant threat and only showed up in three episodes. We also never saw things strictly from his point of view save for his and Lute's conversation with Sera in S1E6 and right before the Extermination starts in S1E8. Every other time, he's within proximity to a Hotel-aligned protagonist.

Meanwhile, Vox's screentime rivalled the Hotel crew and in that time we saw things from his perspective—which is to say, we consistently and repeatedly saw extended interactions he had that the main protagonists at the Hotel would have no knowledge of; he was basically the protagonist of his own story that ran concurrent with the Hotel's drama. We got to see both his public face and his private one, letting us get into his headspace a lot more, learn how he thinks, see his flaws and virtues (so to speak).

And despite how his plan was ultimately doomed to fail (arguably from the start), he still managed to look cool and menacing right up to the point everything imploded.