Shortround6
Major General
They didn't know about the Bf 109F4
Heck, they didn't know about the F-0/F-1 when the decision to put the Merlin XX into the Hurricane was made.
Spitfire squadrons had a higher kill to loss ratio than the Hurricane and just as, if not more, important a lower attrition rate. At least combat attrition.
There were 18-19 Spitfire squadrons for most of the battle compared to 28-31(?) Hurricane squadrons so the total number of kills per type has to be looked at carefully.