Benzyl radical is a very stable radical - and it is easy to see why that is so. There are several resonance forms that delocalize the radical into the ring (draw the structures). This delocalization greatly enhances the radical stability. The excyclic CC bond has a lot of double bond character and its length is 140.9 pm. Of course, several phenyl groups would enhance the stability even further and diphenyl methyl radical can be expected to be even more stable since the radical is in a benzylic position with regard to two phenyl groups.