Do you ever look at various cruise lines or cruise ships and are confused on what to book? Each cruise line has their own benefits and quirks. Some are always more expensive BUT you won't get nickle and dimed to death. Some have a better itinerary BUT you may pay more for that vs. other itineraries.
Do I choose the 7 night cruise or pay a little more for an 8 night? (I would choose the 100 night cruise if I could afford it!)
Regarding a Caribbean cruise, you can choose from Southern Caribbean, Western Caribbean or Eastern Caribbean. Southern Caribbean is affordable but most cruise out of the San Juan port which means airfare could cost more. The western Caribbean cruise will usually be less expensive than an eastern Caribbean cruise. I prefer eastern to western but have done both. The most beautiful port on an eastern Caribbean cruise is St. Thomas. It is breathtaking to wake up in the morning, stroll out onto the deck and see that landscape.
Western Caribbean itinerary best port (to me) is Ocho Rios, Jamaica. Beautiful!!
You see, it all depends on speaks to you. If you're not sure - please speak to a cruise/travel professional and your friends who have cruised before. Keep in mind that they may love a specific cruise line and will be biased against others. This is normal with cruise addicts. I know-- I am one!! Best of luck in your search.