I went thru the same questions!
Recently booked a 4-Day on the Wonder.
Here is what I came up with.
Okay, budget wise, we are limited to a 4-day. I know a three day just wouldn't cut it! As cruise virgins, we wanted to test the waters on a shorter cruise. And, we will be traveling with our son (5). So, there too, a seven day was ruled out.
Next, I have to second ALL the items mentioned so far!
Sure, you can go on Carnival cheaper, but which ship?? No way the older ships that they run on the shorter-cheaper cruises even begin to compare to
DCL! Not in all the photos and reviews that I have seen. Sure they have some new fabulous ships on longer cruises, but there I think you lose a lot of the cost difference too.
Carnival does have an island, Labadee, which they do NOT stop at on shorter cruises... (why you may have thought they do not have an island....) No way I am taking a cruise and not spending a day at the beach!!
Hands down, by all accounts, Castaway Cay is simply unequaled as a private island, at least in all the photos and reviews that I have seen. Nowhere else will you find an adults-only beach, away from the kids and the crowds. Nowhere else will you find a dock at the private island, meaning a big chance that your ship on another cruise-line will not be able to stop there, because they can't tender everyone ashore due to slightly rough seas.
A princess cruise sounds really really super to me! But, without our son... And, when we have the time and money for at least a 7-day, their shortest cruise length.
And, a biggie that hasn't really been stessed yet.
FUN! FUN! FUN!
You know, it is all up to what you are looking for... Non-stop discos and casinos are just not for me... Bleached and Starched white tablecloths and fine china may be nice, but they do not necessarily mean a fun and exciting vacation. Both of these apply especially if you have kids with you.
Good luck with your decision!