Honestly, for us it's a "what else?" kind of decision. I looked into cruises or even staying at a beach resort near LA and just doing a couple days at
Disneyland, but we'd be spending at least as much, and we wouldn't really be getting that much more in exchange. I really wanted to consider a cruise, but prices are crrrrazy for the week we're planning. At least with Disney we can stay at SoG, so we'll basically be spending the same amount as we would have during a less crowded time.
Not that I don't like other places, but since it's New Year's if we want sun, we have to go south, and with little kids we need somewhere that's comfortable to us. I can plan a Disney vacation in 5 minutes, if necessary, and know that it will be awesome. Other places require research...
When I mentioned LA to DH, he asked specifically if he'd be able to go snorkeling (his favorite thing about beach vacations). I told him that we'd have to drive somewhere to do it, or book an excursion, and he lost interest.