The more platforms you support, the larger your potential customer base will be:
Unreal Engine: iOS, Android, VR, Linux, Windows PC, Mac OS X, SteamOS, HTML 5, Xbox One and PS4.
Unity 3D: iOS, Android, Windows Phone 8, Tizen, Android TV, Samsung Smart TV, Xbox One & 360, Windows PC, Mac OS X, Linux, Web player, WebGL, VR (incl. HoloLens), SteamOS, PS4, PlayStation Vita and Wii U.
In this comparison, Unity 3D is the clear winner.
Ease of use.
Unity 3D is known for its easy-to-use interface, which allows new developers to easily create games. Although Unreal Engine has made many improvements in the last update, Unreal still ranks second behind Unity 3D in terms of usability.
Both interfaces are very similar, with toolbars and settings within scalable and movable windows. Unreal’s user interface is quite bloated and complex. In many ways it takes more time than Unity 3D. Importing and saving assets takes a long time and simple tasks require additional steps. Unity 3D’s user interface is very responsive. It is lightweight and runs on Windows XP (SP2), while UE4 requires at least Windows 7 64-bit. Although the final product may look more beautiful in Unreal than in Unity 3D, it can be a lot harder, especially for beginners.
The Unreal Engine has a visual scripting for the Blueprint. A node-based scripting method directly inside. Technically, you don’t have to write code. This is ideal for fast prototyping levels and you can even create entire games with the blueprint. If you’re not a programmer, you can use it to develop games with limitations.
However, this feature is not available with Unity 3D.
When it comes to graphics, the Unreal Engine 4 Unity 3D is far superior. From complex particle simulation systems to advanced dynamic lighting, Unreal Engine has it all. Unreal Engine 4 has the ability to create any visual style you want in 2D or 3D. It’s always good to have the opportunity to further enhance the graphics if you choose to. However, with the upcoming Unity 3D version 5, it’s expected to be close to the Unreal Engine.
Small conclusion at the end.