I had my giant "Two Holidays, One Trip" experience in 2012, going from Oct 30 to Nov 12. We attended the MHP on Halloween night, we did the H'ween tour and the holiday tour, we saw both sets of fireworks, we saw the Soundsational Parade, Halloween "calvacade" (how some refer to the smaller, shorter H'ween parade), and the Holiday parade from the seats reserved by IASWH for tour-goers. We only got to ride IASW and HM in their holiday forms because HM gets converted for H'ween time and IASW was down by the time we got there in late October for its holiday transformation.
I agree with what everyone has said about the Christmas magic, gingerbread beignets, snow after fireworks, and, even there at the start of holiday time on Vets' Day weekend in 2012, the remarkable surge in crowds once the holiday magic starts flowing.
So I'm here to chime in a bit about Halloween time. I loved it. I love fall, so I loved the color schemes. I love the arts and decorations of Dia de los Muertos, so all that in Frontierland added to the ambiance, not to mention the musicians. The Halloween fireworks are a much more elaborate show, meaning a lot more than fireworks and music, compared to the holiday ones, which I also loved. If you like villains, or just the thrill of seeing less common characters, then Halloween is for you. I got to meet a really great Cruella de Vil, who was positively (and hilariously) evil to the CM handling her Meet & Greet. The kids had a ToT experience like no other, getting candy galore in what is already the happiest place on earth, following Ghost Mickeys on the trail, running down the lanes of Tomorrowland instead of merely circling our block, allowed to get in line as many times as they wished.
I love costuming the kids, so getting everything together for a big Halloween where we were really out and about, seeing and being seen, was great fun, with enough excitement to get DH and me to wear our first costumes ever in the 21st century. There really is something magical to being in the parks with so many kids in costumes and most of the adults, too--the only time people over age 12 can do so. I love people-watching and admiring others' craftiness (being myself utterly bereft), so the Oct 31 MHP was real fun. So many people really put a lot of thought, time, and effort into some terrific costumes. I'm not exactly shy, and I love telling people how much I love their outfits and such, so I had a great time complimenting people and finding out more about their costumes. My fave pair was a 20-something couple dressed as Aurora in her Briar Rose outfit and Prince Phillip in the outfit he wears when they first meet (and dance and sing) in the forest. When I told her she and the outfits were lovely, her boyfriend, bursting with pride, told me how she had sewn both herself, working for the entire month. It was a big, memorable night.
We hope to go back this summer, and we live in fear of the weather (much more heat, even though the Santa Anas did bring us two days of 90+ degrees in Nov) and the crowds, of never experiencing Mater's Junkyard Jamboree (the 3yo's fave ride) or the Little Mermaid (5yo's fave ride) as total walk-ons at the right time of day or "only" having to wait 10 minutes for TSMM (the 8yo's fave ride).
So I think the questions for you are more about which holiday will have more magic for your children and you? How important is it to you to ride lots of rides, lots of times? How much patience does your party have for waiting in lines or dealing with less elbow room in some active areas of the park? How much fun do you have with costumes (your own and others')?
Either way, there is plenty of magic and you MUST make the effort to get the seasonal beignets at the Mint Julep.
So I am biased when it comes to what a 4 year old would want.
And since we live in CA we are able to do that.
