I’ve recently sailed both and both have their pros and cons depending what you are looking for. My upcoming cruise with my 24 year old son? Carnival for the better nightlife/party atmosphere. A cruise with older kids? Carnival for the water parks, etc. Want a quieter cruise? Princess. Younger kids would be ok on a newer Princess ship with a splash pad. Princess. I loved the medallion and tbh thought the service on Princess was better IF you go with plus or premium (room service, food delivery to your location, alcohol included in room service). But I did find the overall vibe to be slightly older with less of a night life.