If cabin size is relevant to you, are you comparing apples to apples? Is the cabin size on both ships the same? Not all categories between different cruise lines are the same. If it's not relevant to you as others have pointed out, you need to look at the offerings between ships: food (availability and quality and whether you'll do upcharge restaurants and how much and how often), how much is an additional charge (that you will actually use), how busy/crowded, time in ports (how long and during what hours), shows/movies, lounges, pool size, adult-only areas (if relevant), children's programs (if relevant), tours, etc. Whatever is most important to you, what you will actually use (and have to pay additional for if necessary in order to properly calculate apples to apples). The rest are intangibles that are hard to quantify and are valued differently by different people.
We are able to choose when we cruise (not bound to high season sailing times - no kids) so we are able to avoid the highest cost sailings, thus, we've rarely seen prices that extreme between cruise lines when we want to cruise. Having said that - we also hate cruise lines that charge for every little thing like room service, in-room movies, many upcharge restaurants, etc. It's possible that we might be able to get something similar for slightly less cost but it's annoying to me that some cruise lines try to make up the cost difference by pushing bingo, casino, purchases, drinks and the like. We like Disney's service; maybe it's just as good on other cruise lines but do I want to pay that much and find out that it's not what I expect.
We like adults-only areas and the
DCL tour experiences that we've had and
trust, we like the characters. We like that there are limited areas for smoking and none that are inside like those ships with casinos (this is a BIG one for me). We like that the shows, even the adult ones, are not too raunchy or full of obscenities. We like the first run movies, the 3D movies, and the various other activities that serve our interests.
I'm not interested in dine-anytime cruising. That usually just requires you to book something in advance that day at least or stand in line to wait for a table so DCL's set dining times aren't an issue for me. I like having the same servers every night and I like eating at the same time every night. Unless I have a time conflict, I don't particularly care about having a buffet restaurant for dinner.
There are things I like about each of the DCL ships but I have definitely come to the conclusion that I like the smaller ones. I have zero interest in a ship even larger than the Fantasy/Dream and, given the option, would prefer to sail the Magic/Wonder over those two even though there were definitely some things I liked about the former better than the latter.
Are any of these things relevant to your situation? Every ship/cruise line is different and the experience different.
We've looked at other cruise lines but once I've eliminated those that don't meet those criteria above (bar the character thing), we're left with higher end cruise lines but those tend to require more of a dress-up atmosphere. I'm fine to dress up for dinner either semi-formal or cruise casual (no shorts for me - at least a nice pair of linen or silky knit pants) but when I have to dress like that nearly all day or after 5-6 pm (yes, some cruise lines require that you dress like that not just at dinner but all over the ship in the evening - not to my taste).
Will you get value for the $4,500 difference? Only you can judge that based on actual apples to apples cost comparison but also what is and isn't important for you. In the end, for us, DCL wins out. Perhaps we'll try another cruise line one day, but not for now.
