As someone who's never experienced holidays at universal until recently, I'd say they are better than WDWs offerings. Sure they are the same things year after year but same with Disney. I loved the macys parade and mainheim was awesome for what I saw of it, can't talk about grinch because I only walked through it but it looked awesome online. I personally think Christmas is a weaker holiday in terms of what you can do in theme parks. It isn't like halloween where you can do literally whatever you want with it. They have to follow the typical parade, show and other little things around it formula for the family. Universal killed it with their content, hope to see more in the future
Have you done Sea World? Both Disney and Uni could do a lot more for Christmas. Sea World sets up a whole village with a fire pit, games, food offerings, and Merch. They do a train display right next to the village that is top notch with several trains and buildings including a farm where the animals make noises. The village also drops "snow" at certain times. They do a light show timed to music using Christmas trees in their water area. They have an ice skating show, special fireworks (which BTW, Epcot also adds extra fireworks for the Christmas season), a special Elmo show, a show where animals tell the story of the birth of Jesus Christ and the show has real animals in it, and a special Shamu show that has live singers and a sax player along with water effects and of course Shamu. They used to also have a special Clyde and Seymour show, but I imagine since the animals are still learning the new daytime show they decided to not confuse them with a new night time Christmas show too. Also, most of the places to eat have a special holiday dish (or they did last year, I wasn't paying attention this year) and they give each passholder a free ornament that is different each year. Trust me, both parks could do way more to make it better. It pays off for Sea World too. Every passholder I know goes at least once during the Christmas season and because of the amount of things to do they stay long enough to spend money on at least a meal and a snack. Many like us try to make it out 2 or 3 times because honestly it is tough to do everything in one visit since most of the stuff doesn't start until 2 or 3 PM. For me personally I will always have a Sea World pass coming into the Christmas season. It is the one pass I get every year because of just Christmas alone. The other parks I sometimes will go a year or two without a pass, but never Sea World and mainly because of the holiday (Christmas and Halloween now that I have kids) stuff they offer for FREE.
I still say Disney edges out Uni slightly. But that is because they have more offerings this year I enjoy. It could change next year when they don't have the Osbourne lights and Uni adds something. But right now we have
Candlelight -> Mannheim (Candlelight beats out because it is every night with 3 shows and offers the Christmas story, not just music and lights. It also has different celebrities)
Osbourne Lights - > Parade (I think this is a tie. Again, just personal opinion. I don't need to do either of these each year, but I do enjoy them when I do them)
Santas around the world stories - > Grinch (I go with Santas only because there is more and different ones than just one show, but I could totally see this being more a tie and some enjoying Grinch more)
Decorations at both (Disney for me wins out, their trees and general decorations at each of their parks and hotels is much better in my opinion than Uni)
Epcot has extra fireworks at the end, Downtown Disney has an amazing Santa, and the hotels have things like gingerbread houses. So when you look resort wide you have those extra things too. They also do some extra things at their places to eat like Germany adds a special Christmas thing for the kids where they talk about Silent Night and give out gold coins. It seems more integrated into everything vs stand alone events.
I won't include the Mickey event since it is a paid event and Uni doesn't have any paid events. I am just talking about free stuff in this comparison.
But still when you do a one to one comparison I feel you have to give Disney the slight edge. Now again, if I was ranking all three, it would be Sea World and then about 10 lines down would be Disney and then right underneath would be Universal. The only knock on Sea World is it caters more to the locals and therefore outside of Christmas and Thanksgiving is only on the weekends.