OMB's tone of play depending on his alignment really more or less how he wants himself to be perceived. Town OMB really kinda does not give a shit about having terrible reads or terrible argumentation (read: he's not afraid to enter into long-winded debates) while scum OMB is more concerned with staying alive, buddying up with strong town players, and only tangentially giving an obligatory scum lean/read (read: If confronted, he's more likely to back down unless by someone he's trying to push to be lynched). More or less, he wants to be more agreeable as scum because that's his strategy to survive as long as possible.
Mind you, these aren't totally concrete tells. OMB is an erratic player, but there's a semi-noticeable pattern to his madness.