Parul University

If you're serious about learning how things operate and how the engine's environment functions, Unity is the place to begin. Actually, Unity teaches you how to deal with the engine and code in a very straightforward manner, so that when you delve into Unreal Engine, you won't be overwhelmed by complexity. If you don't master Unity first, I believe you'll be unhappy with Unreal and may even quit up. Therefore, you should first master Unity. The principles are similar across the two engines, with the primary difference being the approach of writing code and attaching scripts to objects in Unreal Engine. You can cut your time spent studying Unreal Engine in half by first mastering Unity.
The second need for learning Unreal Engine and becoming a competent programmer is an advanced understanding of C++. Blueprint is available for your usage.
Contrarily, Unity is powered by C#, whose syntax is straightforward and makes using Unity a breeze.
So, if you want to learn the fundamentals of game development logic, I suggest starting with Unity.