We've sailed both on RCCI and Celebrity...and the passenger demographics are NOT the same. In fact, when sailing the big 3...RCCI, Celebrity and HAL we've found a big difference in ages.
RCCI draws more families, groups, teens, etc.
Celebrity...slightly older...not as many young families.
HAL...fewer families...(maybe too because cruises tend to be longer)
Like Norm said, you should sail on the line that you feel most comfortable...