Have you considered doing your 2D game in 3d but just set the camera up to look down or sideways at the world. As long as you keep the models you use simple or even use sprites you can get the benefits from 3d like parallax, shadows, lights for free that you may have to work at recreating in your 2D game.
But it depends on your target platform, if you’re going mobile then 2D would be a good option.
I’m new to Unreal (about 4 years with Unity) but my understanding is that it’s project build size can be larger than a Unity game, this might be something you want to consider.
But why not try both hunt down tutorials on making 2D games for both and give them both a whirl, but take these mini games all the way through to their target platform then compare both.
You should have a good idea what you find easier to work with and what they produce.