Both Unreal and Unity have their advantages and disadvantages.
Unreal is pretty much time consuming (slow/long compaling shaders, crashing, bugs, slow loading…), have different learning curve while I start to work in Unity almost out of the box.
Also, Unreal landscape and foliage rendering always annoyed me (for example some leaves, trees, grass etc are disappear and appear in front of your eyes). It can even be seen in AAA games when you pay attention. It has always been like that in Unreal.
Unreal is more complex than Unity and Unity have more advantage in developening mobile games.
For example advantage in file size - almost the same project in Unity takes ~40-60 MB while in Unreal it was ~200MB