I usually keep NPCs' stats hidden from players, but in this system I can see some upsides to showing the players these stats. I like the strategic choices that result from the dice system, and I can imagine that these choices would be more interesting if the players had more information (for example, they could make better-informed decisions about when to spend Threat to inflict strain on NPCs).
How much do you show your players about NPC stats, and why?