The major difference is that the Shia believe that there is no book of Hadith which is 100% authentic, and that all hadiths must be checked against the Qur’an and the established principles of Islam. In contrast, Sunnis believe that certain books, such as Sahih Bukhari and Sahih Muslim, are 100% correct and unquestionable. These books, however, obviously contain some Hadiths which go firmly against the principles of Islam and cannot be justified in any way, and therefore their claim is proven false through the content of the books themselves.
For more information, you can refer to Sheikh