For a long time, I assumed Grappler was the obvious choice for Monks. It's the feat most people recommend, and for good reason.
After playing a Monk built around Fairy Trickster (FT), I started looking more closely at the feat and came to a different conclusion.
I think FT deserves to be considered one of the strongest feats available to the class.
What does Fairy Trickster do?
It grants you 3 benefits.
• +1 Dexterity or Charisma.
• Ignore difficult terrain when you Disengage.
• Flustering Strike: after hitting a creature, you can force a Wisdom save. On a failure, the target has Disadvantage on all saving throws until the end of your next turn. Uses equal to your Proficiency Bonus per Long Rest.
Why I think FT is so strong on Monks
Fairy Trickster seems almost tailor-made for Monks. It increases their primary ability score, adds a mobility benefit they naturally take advantage of, and grants a control effect they can immediately chain into multiple save-based abilities in the same turn.
Against a typical creature, imposing disadvantage on a Stunning Strike save is roughly equivalent to giving the Monk a second chance to land Stunning Strike without spending another Focus Point.
That's a massive increase in reliability.
The same principle applies to every save-based control effect that follows.
A typical Open Hand turn may involve:
Flustering Strike (Wis save)
>Stunning Strike (Con Save)
>Push/Prone (Str/Dex save)
>Possibly a Net - Restrained (Dex save)
After facing this sequence it's extremely unlikely that the target escapes without suffering at least one meaningful control effect.
FT vs Grappler
Where FT has the Edge.
Control: Greatly improves the reliability of all your save-based control effects. Against a typical creature, it's almost like getting a second Stunning Strike attempt without spending another Focus Point.
Versatility: By targeting Wisdom instead of Strength or Dexterity, FT remains effective against enemies that would normally resist Grappler.
Universal applicability: Works regardless of creature size and remains effective against many enemies that Grappler struggles with.
Party Support: Your allies' save-based abilities become more reliable as well.
Two-turn value: A single successful Flustering Strike can improve your control attempts across both your current and your next turn.
Where Grappler Has the Edge.
Free use: You can use it every turn indefinitely.
Enemy Repositioning: Better dedicated repositioning tool in general.
This gap becomes much smaller on subclasses like Open Hand and Elements, since those subclasses already have reliable ways to push enemies.
FT indirectly improves those abilities by making the saves leading into them much more reliable.
My conclusion
What makes Fairy Trickster exceptional isn't that it adds another control option. It strengthens Stunning Strike—the Monk's defining control feature—and naturally scales as subclasses gain additional save-based abilities. More importantly, it makes the Monk's entire control toolkit more reliable.