Why is benzylic free radical more stable than allylic free radical?

This is due to more resonance of benzylic free radical.

While allylic free radical has only two resonating structures soit has less delocalization.

However, you are ignoring the fact that , allylic free radical too, can show 4 rsonating structures, because of hyperconjugation , AND , thermodynamically, too, ALLYL FREE RADICAL is MORE STABLE by 2kcal/mol .

This is due to the fact that Benzylic free radical has more no. of canonical structures as compared to Allylic free radical