See explanation below:
When comparing two acids , we look at their conjugate bases stabilities and compare them.
A strong acid will give a stable conjugate base , so the reaction is favoured in the forward direction (acid dissociation).
Looking at both conjugate bases, we can see that the negative charge is carried by fluorine for
Since fluorine is a more electronegative than carbon atom, the negative charge will be more stabilized on fluorine and thus