Being a TA and having been on 3 cruises, I highly recommend a good TA. Only because a good TA can give you some really good tips and advice and should be cheaper then going through Carnival. Not to mention reality, like saving chairs is not allowed,
it is not enforced at all. So where do you go when you can't find a seat? My husband and I could not get one on deck either days at sea, even though 50% of the chairs were empty. Well, they had a sandle on it or a towel and had been empty for a couple of hours. So we found a nice quiet spot to sit and would recommend it to all our clients along with how to get a chair there. Not to mention how to get excursions cheaper etc.
So what ever you choose, have a great time and enjoy!!!