Nice mood in your video.

There's no particular reason why to pick either 2D or 3D. It depends completely on the artist, who wants to do it. I only hope that the same outlook can be achieved both in 2D and 3D. Say that a 2D artist draws a beautiful cute reindeer calf. It can easily be done too complicated to be transfered into some 3D modelling software. Or the other way around. A 3D animation artist might concentrate on creating a recognisable reindeer that can easily be programmed, but forgets to actually create something uniquely interesting in the visual appearance, so that when the reindeer is drawn as a simple 2D contoured cartoonish character, there is nothing interesting and appealing in it.

As I said, that reindeerr in the project pic is doen with Anime Studio. You can see the handles there. It's not a very good one. The body is too long, which makes him look like an adult reindeer. I could shorten it a bit and render the small animation of him walking, just to work as a motivator for anyone.