How are reactivity and dipole moment related? Recently, I came across a question:  which of the two compounds has a greater reactivity; $\ce{NH_{3}}$ or $\ce{NF_{3}}$?

It is known that despite the same structure the dipole moment of $\ce{NH_{3}}$  is greater because of the electronegativity difference. So, I though that the reactivity of $\ce{NF_{3}}$ should be more as it is easy to break the bond due to the high electronegativity of fluorine but the answer turned out to be $\ce{NH_{3}}$ and I can't figure out why.
The reactivity of amines is generally based on how nucleophilic they are.  In turn, their nucleophilicity is dependent upon how much of the nitrogen lone pair of electrons really exists on the nitrogen atom (e.g. the lone pair electron density on nitrogen). In ammonia ($\ce{NH3}$), the lone pair electron density on nitrogen is very high making ammonia quite nucleophilic, quite reactive.  In the case of nitrogen trifluoride ($\ce{NF3}$), the three extremely electronegative fluorine atoms inductively remove much of the electron density from nitrogen; therefore $\ce{NF3}$ is less reactive than ammonia in a nucleophilic sense.