But is exactly what the Blueprint system is for, and engine source is in C++. Blueprint is fast, it executes quickly enough, it compiles almost instantly so it’s perfect for prototyping. Most importantly, it’s understandable by virtually everyone who understands game logic. It’s artist friendly and powerful, sure it has a lot of bugs right now but I betcha it’s more bug-free than Mono integration. I also bet that Blueprint has more things from the engine exposed to it than C# does right now too, because it was integrated at day one.
C# only serves to mix up the flavours even more and add a third language to the mix, which in itself is going to have it’s own squirms and problems. C# will only ever serve as an interface between user and engine the same way Blueprint does, at which point I believe you are wasting time you could be spending learning new things, that will ultimately make the experience of working with the engine much smoother and you’ll have less roadblocks in the way too.
The only reason C# plug-in exists at all, is because Unity uses it, and somebody knows they can make money bringing it’s users over to Unreal. It’s nothing to do with the pros and cons of the language, you will always be better off using the native code of the engine. Either way, you’ll have to learn the engine, so why not experiment with C++ more too?