Auto Loan: Joint or Self?

I am applying for an auto loan (~$15000) from Capital One. I want to know if it would be advantageous to apply for the loan with my fiancee as a joint applicant. I know that my credit score is close to 750 and my fiancee's score is close to 720. However I have more than 5 years of credit history and she has only a year of history. My annual income is around $33000 and her income is around $17000. Should I apply by myself or should I submit a joint application to get the best rates? I would appreciate your comments on this. Thanks guys.