Answer
$NaOH 0.20M$ will have a higher pH.
Work Step by Step
When comparing 2 base solutions (with the same concentration), the one with the stronger base will have a higher concentration of $[OH^-]$.
- In this case, since NaOH is stronger than $NH_3$, it will have a higher concentration of $[OH^-]$
With a higher concentration of $[OH^-]$, it will have a lower pOH.
With a lower pOH, it will have a higher pH.
