UE4:

► Game logic is written in C++ or blueprint editor

► Base scene object- Actor

► Input Events- Component UInputComponent of Actor class

► Main classes and function of UE4 includes int32,int24, Fstring, Ftransform, FQuat, FRotator, Actor and TArray

► To create a new instance of a specified class and to point towards the newly created Actor. UWorld::SpawnActor() may be used

► UI of Unreal Engine 4 is more flexible and less prone to crashes

► It does not support systems like X-box 360 or PS3, it requires AMD Radeon HD card to function properly

► Less expensive compare to Unity3D

► To use UE4 you don't need programming language knowledge

Unity3D:

► Game logic is written using the Mono environment

► Base scene object- GameObject

► Input events- Class Input

► Main classes and function include int,string,quaternion,transform, rotation, gameobject, Array

► To make a copy of an object you can use the function Instantiate()

► The asset store of this tool is much better stacked than UE4

► It supports wide range of gaming consoles like X-box and PS4, as well as their predecessors

► Unity3D has free version which lacks few functionality while pro version is bit expensive in compare to UE4

► It requires programming language knowledge.