The original Delta6 (this is just the business card edition) was inspired by Cthulhu Dark and 3:16. The idea was to get a fully functional generic system to play anything I want. It has been play-tested by a good friend of mine and works well in practice (when Blades in the Dark was published, I took it as the confirmation of what I’ve suspected and you have just mentioned: the probability distribution is really nice).
T3CS, on the other hand, is an exercise of minimalism. I’m kind of allergic to arbitrary rules and one day I wondered how a system without them will look like. Lots of rules that we currently see as natural are, indeed, quite arbitrary if you think about it: why d20? why d6s? why hit points? why initiative?
So I selected the most basic elements of a shared narration:
- There is conflict: So we need success & failure.
- There is drama: So we need the notion of partial success/failure.
- There is uncertainty: So we need randomness (although I admit that this is questionable).
- Not all character/circumstances are equal: So we need the notion of advantage/disadvantage (a generalization of stats, mods & difficulties because, well, at the end of the day they all are the same thing mechanically).
Mix all these elements with the Czege Principle (so you need to determine the narration rights in the most interesting way) while trying to avoid any arbitrary decision… and what you get should be pretty close to T3CS.
Regarding your comment… the bland distribution of T3CS has several advantages:
- Being so coarse grained, it makes clear that this is not a simulationist system and that you should get your realism from the narration rather than from the system. I think that this is the only way to go when you want a truly generic system, because simple models are more robust and less prone to be interpreted as anything but the crude version of reality that they are (all RPG systems are crude, T3CS just doesn’t pretend otherwise).
- Partial successes/failures are the most realistic and dramatic outcomes. In T3CS they automatically are the most common outcome in all situations.
- You already have everything you need to play in your pocket.
This being said, I believe that the heart of the system is in the narration rights assignment rather than in its probability distribution. I mean, you are mainly deciding who gets the narrative power and that person should use the total/partial success/failure outcome as a prompt (see Other Skylines for similar implementation of this idea).
Anyway, this system does not pretend to be anything but a simple way to improvise games on the go, which is the main niche for business card sized RPGs