The Land/Sea would never work for us because 3/4 days is just not enough time in the parks! We are not sure if we will like cruising or not, so we are trying the 4 night Wonder for our honeymoon. I really don't see any advantages to Land/Sea except for the transfers and one check in. Even if you want to only stay at WDW for 3 or 4 days, it may save you money to book things separately (plus you will have more choices for your accomodations).
For our honeymoon, we are doing 4 day Wonder cruise, 3 nights at Universal, then 6 nights at WDW. I am stressing that we won't have enough time to see things AND relax at WDW with only 6 nights, but we really wanted to try Universal. I have a feeling that I am going to get hooked on the Cruise line and Universal as well! I think the land/sea has a lot of limitations, but for some people, it is easier for them.