While Sunni and Shi'i ritual law is quite similar, there are occasional differences due to differing interpretations of the Qur'an, the use of hadith compilations not used among Sunnis, differing opinions on the reliability of various hadith or hadith narrators, different historical scholarly traditions, and slightly different approaches to the principles of jurisprudence (for instance, Shi'is do not use qiyas whereas some Sunnis do; there is a different view on what constitutes ijma'). 

However, even with some subtle differences, the basic idea of ghusl - as a major washing in some circumstances as opposed to wudhu - is the same.