My kids are 4 and 5. In October we spent a week at WDW. In Feburary we took a four day cruise. DL is different than WDW, but with kids it will map out ok.
The kids really enjoyed both. But the experiences were rather different.
They love the attractions at WDW and the POOL! WDW was a week of getting up early, running two children around the park until sometime after lunch, spending the afternoon with two children in the pool (too little yet to swim in the deep water by themselves). We were with our kids almost 24 hours a day. There was always something to do - maybe too much. We had a wonderful time, and arrived home exhausted.
The cruise was very different. Although the stateroom was small, the curtain (and exhausted kids) made sharing the room ok. The enjoyed the pool and the kids clubs. Meals were much more leisurely. They loved
Castaway Cay. There was always something to do, but the something was often "sit in a deck chair." Cruising - even cruising with kids - is more leisurely and elegant.
My kids say they like both, forced to choose, I think the appeal of rides at this age (and a big pool rather than the little ones on the ship) would win out - but they did enjoy cruising. And honestly, I prefer WDW to a cruise - more to do, I don't feel so dependant on calm seas and nice weather (we lucked out with both), and I have more control over my own "value" (don't want to pay for big meals, don't - unlike the cruise where the cost of eating and kids clubs is built in). But the cruise was much more adult and much more relaxing - and since the kids didn't mind, we will do it again.