As a Frenchman who speaks Italian and know Italy well, i'd say that Corsican are ethnically Italian but culturally French.

The Corsicans speak a dialect that is very close to some other italian dialects and they have italian surnames (Paoli, Casanova, Mancini,...). They are as close to the Italian nation than Sardinia or Sicily. But because of the French assimilation system, they've lost their language and were educated the French way.

Interestingly Corsica is famous for producing two kind of people : policemen and gangsters. There are indeed many corsicans in the Police (including at a high level position). As you can imagine, sometimes these two worlds collude...