Unity advantages:
- Lower computer requirement for the editor.
- Better for mobile development.
- Better for 2D (but many other engines are even better).
- A bit easier to make low requirement games.
- C# easier to use than C++
- More stuff in the Unity store.
Unreal advantages:
- A more complete package, less reliant on additional purchases.
- Easier to get high end graphics.
- Blueprints is easier than C# and a great complement to C++ for more experienced developers.
- In my opinion a more fun company and community to interact with.
- A bit higher average qualty in the store.
Both are comparably easy to use. Unity has a clear edge on mobile 3D games. But for PC (and consoles) I belive UE4 is considerably better for even a beginner, and the gap widens the better you get and the bigger game you make.