While they are addressed in the crafting thread difficulty mods can apply to any roll. They are particularly useful in comparing the quality of an action. Like Skills or Attributes, difficulty is assessed on a scale from 1 to 5 (nWoD, p.124) from 0 (Easy) to 5 (Sorely Tested).
  • Difficulty always trumps Successes. 1 Success with a -1 Difficulty modifier is 'better' than 3 Successes with no modifier. Why? Because the action attempted was purposely a more exceptional effort than the most basic version. If an ice skater simply jumps, no matter how nice that jump is, it's not as impressive as jumping... with a spin.
  • This also allows experts to leverage their pools in a more meaningful way than leaving results totally to (albeit weighted) chance.
  • If the Difficulty is the same, then number of Successes are compared.
Exceptional Successes rolled elevate the Difficulty by one degree for cases of comparison. An easy task is done with flair or remarkably well and so on. Example:

Jack rolls 7 Successes on Easy Mode (0 Modifier) to fetch a pail of water.
Jill rolls 3 Successes on Minor Difficulty (-1 Modifier)
- Jack rolled an E-Suxx, moving his action into the same difficulty class as Jill's
- The class upgrade 'costs' 5 Successes, leaving Jack with 2 versus 3 for Jill. Jill wins.

The Reverse Is Also True

If you roll for an action with no penalty, you accomplished an easy action. The Devil Is In The Dots. The ice-skater didn't do a triple-axel even with an Exceptional Success on a 0 Modifier. Please don't over-narrate. Take an appropriate penalty.

The Math

Yes. It's cheaper to declare a Difficulty.
-1 is more advantageous than .33x percentile.
-5 Successes to upgrade difficulty class is hella expensive.

This is by design. It's the reward for assuming risk rather than just reaping the reward of chance.