Just skipping over the last few days of posts as I remembered something that was important to me at least about this overall topic.
I like details, details the players can latch onto to include in their plans, mention in their approaches to problems, use to better understand the world setting. Details that constrain their options so they have to get creative, as well as change up their approach or use methods or resources they might not normally. I want details that give them examples and ideas beyond what they may have on their own.
For combat, this sort of detail has in some games come in the form of hit locations, and variable weapon performance against types of armor. Different moves based on weapon type and reach, different defenses based on mobility, and of course differences based on fighting styles and or feats and advantages.
I want that sort of thing so my players, doing what they do the most, which is interact with entities and mysteries, so they can have details and nuances to what they do, what they have prompts for.
However, I run games with a lot of ST attention, and the NPCs are with interacting with. I am fairly sure that this is not the case on MU*s, at least not to any degree of detail.