We are taking an MSC cruise out of Rome next March for spring break.  The way our travel days/flight times will most likely work out means we'll get there morning or midday the day before we get on the ship (ideally we would get there 2+ days early but with school schedules we just can't make it work).  From the map it looks like it's roughly the same travel time from the airport to Civitavecchia or Rome.  Does it make sense to go into Rome for roughly 24 hours and then to the cruise port from t