Quite a few of my ancestors have different names on census returns, either the first or 'middle' name, or a shortened version of any of their forenames. I record them with the name on the birth registration or the baptism, then make a note of the variations and where they occur. I find it quite interesting to see how the census returns have been filled out; one year a family is recorded with all their names in full, especially useful in filling in initials from birth registers, then another year they are all recorded with what is obviously just the name they are known by on a day to day basis.