My wife and I have done a lot of comparing along thes same lines and I have to admit that either a Cruise or an All Inclusive to the Carribean can be very expenxive, or done on a lower budget. There are several factors to consider, time of year, vacation provider, destination, and as far the cruises, what cabin you choose.
It is not really fair to compare one to the other, since one person's great vacation is just not the other person's cup of tea. We have done both and have enjoyed both just the same. I love setting on the beach day after day while my kids stay busy with hotel activities at the All inclusives, but I also enjoy the excitement of setting sail, waking up to different ports, and watching all the people around the deck.