Some days, it's hard to tell. Fer ex...
Although I admit even my examples were distinctly imperfect.This isn't about the effort to plod through a rule itself, long division to get the dice result or a table lookup aren't part of this they're the rule in action and being applied. This is about the amount of effort put on the GM, by the game mechanics, before and after actually getting to roll a die and get a result.
My intent is/was about the "rules about the rules" and how much effort, and perhaps fiddlyness or work or fragility, there is in those. I'm not trying for a full "joules required to run a session", or even "joules required to use a rule", but more "joules required during session in order to use the rule". With the assumption that the rules are being used correctly.
I'm afraid I can't speak to BitD or Fate or anything. They read very nicely, I've cribbed a couple prep & story methods off them, and the SR hack I ran across looks intresting. But local rpg culture is... we'll be nice and say "allergic" to those hamburgers.
Would do more but on mobile & family time incoming.