I have played a couple of PbtA games, know just a bit about FATE, and basically nothing about Stonetop, other than that posters who are known to be proponents of narrative mechanics-filled games seem to be fond of it.
The posters I see talking most often about Stonetop are
@Manbearcat and
@hawkeyefan. Neither is a proponent of "narrative mechanics-filled" games - I'm not 100% sure what a "narrative mechanic" is in this context, but I take it to mean something like "spend a point to make X true of the fiction" and the PbtA games that Manbearcat and hawkeyefan talk about typically do not have such mechanics.
The descriptions of the
mechanics in Stonetop are very similar to those in Gygax's DMG: roll some dice, add some numbers, to get the result.
The difference from AD&D consists in
the principles that govern the GM's statements about what happens next.
The factor that is most relevant to be me is that all those games, to my limited understanding, use game mechanics to facilitate telling a particular kind of story. This is a concept I don't generally find fun, so I am generally not interested in playing these games. If I'm wrong about that basic concept I apologize and will happily accept correction
Yet I feel we have had this same conversation dozens of times, your misunderstandings have been corrected then, and still here we are again!
The core of the difference between AD&D and Stonetop is not mechanical. It's about the principles that the GM follows.
If you try to apply the Stonetop principles to GMing AD&D, you'll quickly run into problems with some of its mechanics - they don't fit with the principles. The reverse is also true: if you try to apply AD&D principles to Stonetop, you'll quickly run into problems with some of its mechanics. In fact I've read posts about this very sort of issue on these boards - eg a GM who applied AD&D principles concerning
GM authority over, and flowing from, secret backstory to adjudicate the DW move Discern Realities which then meant that they had no hard moves to make when their PCs failed Discern Realities checks.
But in both cases its the principles that are primary, and that create these constraints. And there are some RPGs in which a given set of mechanics can be toggled between principles: I've often posted that I GM Classic Traveller using a version of AW/DW/Stonetop principles. Cthulhu Dark is another example: it is written to be GMed using principles very similar to AD&D ones, but when I GM it I use principles very similar to Burning Wheel ones.
I am not asserting that there are no RPGs with interesting mechanical differences. Nor that some of those mechanical differences
in themselves produce profound differences of play experience (compare eg AD&D, or Rolemaster, or Burning Wheel - on the one hand - to Marvel Heroic RP - on the other). But I don't regard Stonetop vs AD&D, or Burning Wheel vs AD&D, or even Cthulhu Dark vs AD&D, as examples of this. (Except perhaps in their lack of an AD&D-style spell system - but this actually means that they have
fewer "narrative mechanics" than AD&D, given the way AD&D spells work!)
While I agree that simulation can never be perfect, I'm a whole lot more optimistic than the quoted post that it can be done well enough for rock'n'roll.
The goal isn't necessarily to simulate the fantastic reailty to a T, it's instead to simulate it to the point where the GM and players are all on the same page in feeling like the characters are inhabitants of an actual world or setting that exists beyond them and could in theory exist without them
By this measure, every RPG I've played since I was about 15 is simulationist. Which would make the term functionally useless.
What distinguishes Rolemaster from Burning Wheel is nothing to do with the "reality" of the setting. Certainly not its depth.
What distinguishes them is the principles that govern how
what happens next is decided.