C++ is antiquated and clunky, it compiles into fast an efficient executables though. This makes it hard to learn and slow to develop in but it produces very fast code. The UE API is fine, the documentation is sparse in places but quite descriptive for the commonly used features.
C# is a well designed modern language, it’s executables are not as fast as C++. It’s easy to learn and more productive due to its more modern syntax features.
Both languages have there advantages and disadvantages. So it’s really subjective to the coders needs. So no matter what people argue about on this subject, no one person will ever have a 100% correct reply For c# vs C++.