Consider these two examples:

神｛かみ｝を信｛しん｝じるの？

and

神を信じますか？

To me, both mean 'Do you believe in God/gods?', with the first example possibly slightly more casual than the second. Other than that, are there any other nuances? I can't really give a context, but in general they seem to be used slightly differently and I can't seem to pinpoint the exact differences.