You got me interested here: what are the main differences between Princess and DCL?
There really wasn't much. And the extra Disney perks DCL has, to me, isn't worth $3,000. It's not even worth an extra $1,000 to me, at least, not for a cruise.
My DD is 14, so she doesn't need all the Disney stuff any more. She still loves WDW and we are going to DL next summer and she is excited about that, but on the cruise, she didn't need it. She said this cruise was her favorite vacation EVER! (gasp)
I will list a few differences that I can think of. I'm comparing the Dream to the Emerald.
The staterooms - I like the size and layout of Princess's mini-suite better than DCL's verandah room - I didn't feel squished like I did on the Dream. I like that the sofa bed is a pullout sofa on EP instead of the flip bed on DCL. I prefer DCL's split bathroom, though.
Food - Comparable between Princess and DCL, but I liked Princess a little more. I liked the MDR dining and food on Princess more than DCL, but I liked the buffet better on DCL (peel-and-eat shrimp). I liked the desserts better on Princess (lacked flavor IMO on DCL). And the pizza on Princess was soooooooooooo good. I couldn't walk by the pizza place without grabbing a slice (NY style thin crust, so good). But I like the soft-serve ice cream better on DCL (more flavors and self-serve).
Entertainment - our last DCL cruise, we didn't see the shows. To me they were one and done. Princess only had one musical-type show and I wish we hadn't wasted our time on it. DCL wins in the entertainment category by a landslide (not really a surprise there). The random musicians are also a lot better on DCL than Princess. One night, we were watching a live band and the singer was reading the lyrics off of an iPad. And still getting some words wrong! It was sad all around, except they had a nice Dixieland Band we enjoyed, but they only performed once. We don't cruise to watch live shows, though. We see those at home. When we cruise, we enjoy excursions, meals, and our verandah.
Embarkation & Disembarkation - Princess was seamless and fast, DCL was slow and blah. We boarded Princess around noon, walked right on, and our room was ready when we arrived. Same when we left - after waiting for our time, we walked right off. Luggage was quick and painless and customs was a breeze.
Staff - We liked Princess better. On Princess, they seemed to truly like (and some LOVE) their jobs. Every server (MDR and buffet) and bartender we encountered were friendly and helpful.
If you have any specific questions, don't hesitate to ask