It is hard to avoid comparisons, and Arkane are best known for their Dishonored series, considered a breath of fresh air and groundbreaking for both immersive sims and the stealth genre, as well as being beloved for its characters, setting, and worldbuilding. Both games have their strengths, and there are clear areas in which they outdo the other.
Spoiler warning: This article contains spoilers for both Deathloop and the Dishonored series.
Part of why Dishonored's stories are so beloved are for the vile villains the heroes are sent up against. From egotistical inventors, to corrupt leaders of a church militant, to fearsome witches, Dishonored's villains manage to make big impacts on both the stories, and the player themselves, despite their often-short screentime.
By contrast, Deathloop's Visionaries simply don't quite have the same luster, in part due to the game's openness preventing major villain twists like the betrayal of the Loyalists in Dishonored. Only Julianna has anything like as much impact as a Dishonored villain, and even this only becomes apparent towards the end of the game (or in multiplayer). In particular, the game lacks anything equivalent to the Outsider, one of Dishonored's most iconic characters.