'corpse' is more a legal/scientific/medical term for a body.
In general conversation you'd almost always use the term 'body'. It sounds much more polite and caring. 'corpse' sounds rather cold or remote as the term does not carry any sense of emotional attachment of the speaker to the 'body'. 'body' doesn't always carry this sense of emotional attachment or caring, but it can. Corpse is far more distant and colder a term.
As an example, if a friend died, you would never use the term 'corpse' yourself. However the medical examiner may use either term - 'body' or 'corpse'.