One nice thing about the Disney Cruises are that if you like to visit characters, you will meet more of them and more frequently with little to no waiting time for many. For example, my 20 year old brother got a picture with at least 5 Disney princesses just because he could. They would be wandering about the Atrium, no lines, just wandering, and so they'd stop for a picture with whoever asked. Same for other characters. Some of them will have lines (Fab 5, Jack Sparrow, etc) but until my first Disney cruise, I had never met so many characters as I did on the cruise compared to walking around the parks.
Oh, and the food is AMAZING. Super friendly for allergies!!
Honestly, if you really can afford it, do the Disney cruise. Disneyland/World are more affordable, but also I think easier to visit because you can go for just a day or 2, whereas a cruise can take 3-7 days. I would also recommend cruising the off season and trying to share 4 to a cabin if you really want a good price. I shared with 3 family/friends and we got a balcony 7 day cruise to the Caribbean for $1250 a person. Sounds steep, but try and find that same price; it's practically impossible. We did a 9 day Alaska ocean view for $1250 a person, too.
If you have questions, feel free to ask! I am most knowledgeable about Disneyland and cruising, thought I've been to WDW 2 times in the past 2 years.