I haven't cruised Disney yet, but I will give you the reasons why DH and I chose Disney for our family cruise next year!
Just this summer DH and I took our very first cruise aboard a
Royal Caribbean ship. It's not one of their mega ships, in fact, it was aboard the Nordic Empress, which is their smallest ship. Small, but classy. We LOVED that cruise and that's what got us hooked on cruising.
We decided that next summer we'd cruise and take DSs with us. So I began to research all the different cruise lines and ships, to see which would suit all of us the best.
*Disney has the LARGEST of cabins of all the cruise ships out there.
*Except for cat 11 and 12, ALL of Disney's cabins have the split bathroom which will be great for us, since we'll be sharing 1 cabin.
*You rotate through THREE dining rooms, not just one. AND your waitstaff rotates with you.
*You have the option of MANY adult-only areas on the ship, such as Palo's restaurant, Quiet Cove pool, and after 9pm the night clubs are 18 and over only. This is strictly enforced on the Disney ships, and NOT strictly enforced on other ships. In fact, most other ships don't have an adults only pool or restaurant. On the Nordic Empress there were always kids in the hot tubs, on the Disney ships the adults have some hot tubs just for them!
*Adults only beach on their private island,
Castaway Cay.
*Beautiful ships....elegant, classy, not harsh or gaudy. Outstanding theming in all areas of the ship!
*We feel Disney will have the best programs/teen lounge for our DSs who will be ages 16 and 13 when we sail next summer. This was a BIG consideration for us, since we wanted to make sure the kids have as good of a time on the cruise as we do. I trust Disney's standards to provide a suitable atmosphere for our DSs.
*Teens-only excursions which our DSs will love. No other cruise lines provide teen-only excursions.
I could go on and on but these are the main points which made it so easy for us to decide on a
Disney cruise 
We live near Boston and have a huge choice of other cruise lines, which would NOT require us to have to fly (between Boston and NYC ports)...but we feel so strongly about the quality of the
Disney Cruise Line that we're willing to fly to cruise this line.