I'm actually super curious as to why you have that opinion, UnrealEngine has been around longer, and has always had significantly more in the way of production quality tools and features. There are certainly differences, especially when you get down into the details, but two large features Unreal has had for 10 years, shader graph tools, and animation blend trees, are either new and still painful in Unity (mechanim) or only existent as a third-party add-on (shaderforge)