I've been on many, many cruises. As for which line to take, it all depends upon what it is you're looking for. Each and every cruise line has its own distinct brand identity. Each of those brands has a certain "style". These "brands" and "styles" tend to be very consistent on all the ships in these lines. They also vary very much in quality. Each line also tends to attract a certain type of passenger. For example. Carnival is known for catering to a "younger" "wilder" crowd. From my experience, depending on when you go, this can mean lot's of children running around, lot's of low class, rude people, allot of drunks, etc. On the other hand, if you're looking for fun, the Carnival crowd can also have more energy. (i.e. more people in the casinos, more lively environment, more fun and rowdyness at the shows, etc." They are also very "straight".
On the other extreme are lines like Cunard and Seabourne, you can also add in a line like Windstar. These lines cater to not just an older, but a more affluent crowd. They are quieter, more sophisticated and of much higher quality. The foot will be better, the service will be better, the shiops will be more elaborate, whether that is in the Cunard style of Old World Elegance or the Windstar Style of "casual, understated" elegance.
"Just Below the top end are lines like Holland America.
Of all the lines, my favorite is Princess by far. They have beautiful ships, quality service, nice size cabins, lot's of amenities, great food and reasonable prices. The crowd will be on average about 10 years older than a Carnival. The will also be more sophisticated, perhaps more "evolved". Royal Caribbeen is also in this class, with perhaps a bit younger crowd and a bit more of a family environment.
I could tell you lots more, but this is obviously a limited forum. Feel free to e-mail me directly if you'd like to talk about it more. I'm sure I could give you a good insight into what expect from whom and also where to get the best deals on cruises.
Good sites for deals?
and belive it or not, "Sams Club Travel".
Feel free to contact me directly if you want more specifics. Tony. firstname.lastname@example.org