Is fluorine more reactive or less reactive than chlorine?
Fluorine is clearly more reactive than chlorine. It is arguably more reactive than any other element on the Periodic Table.
Electronegativity increases across a Period (from left to right); and decreases down a Group. Fluorine is thus the most oxidizing element on the Periodic Table; it is thus the most reactive element on the Periodic Table. Fluorine chemists tend to be a breed apart. The older ones may have a few fingers (or eyes) missing because of the hazards of experimental fluorine chemistry.
As a follow up question, consider the elemental oxidation states in the (real) molecule