Answer
The magnitudes of the fields at P are equal.
Work Step by Step
We can write the general equation for the magnitude of an electric field:
$E = \frac{\vert q \vert}{4\pi ~\epsilon_0~r^2}$
Since each charge is the same $-q$, and the distance $r$ from each charge to point P is equal, the magnitudes of the fields at P are equal.
