I would be really surprised if it was more. While my experience with Unreal is limited (I had to make a few small games in it as a part of middleware course on my Master's gamdev studies), it was one of the worst user experience I had.

Now, I love Unreal, and I'm really regretting not getting into it sooner before getting so used to Unity. But Unreal has the following problems, which makes it a not-so-good choice for Game Jams:

My experience with Unreal has been soo slow. If you're working onsite, chances are that you only have a laptop. Even though I had a pretty OK laptop at the time, everything was loading for literal minutes, and just opening the project meant I had to wait for a pretty long time. Unreal is just pretty heavyweight - which makes it an amazing engine for larger games, but not for gamejams.
As far as I know (which may have changed), it's not really made with 2D games in mind, unlike Unity. I'm not sure if you even can have 2D Physics and collision system. Which is another problem for Game Jams - making a 3D game is simply a lot harder, especially if you don't have a 3D artist in the team.
The games you get from Unreal can get huge in size pretty easily, which also makes sharing them and convincing others to play them a little bit harder.

Those are the reasons why I personally wouldn't choose Unreal. But it's based on my experience with it from few years back, so some of it may have changed. But I'm biased since I've always worked mostly in 2D - and if I ever wanted to make a 3D game, I'll definitely rather choose Unreal for that. Because the 3D projects I'm working on at my job that are in Unity is just frustrating experience.