Most affordable would certainly be Carnival, but are they also the best? It depends on what you are looking for. Carnival tends to be more of a party cruise, and if you like that, then maybe it is best. My personal opinion is that Royal Caribbean is best overall. They cost more than Carnival, but there is so much more to do on them, besides partying, and the ships are much nicer. I wouldn’t rule out Carnival, but I think if you go on RC first, then go on Carnival, you will be a little disappointed, whereas the other way around you will be pleasantly surprised.