Thanks for your response. Yeah, it's hard to tell, though I would still expect it's going to be slower - C# wins not because it has a superior native codegen (it's probably a bit less efficient, since JIT is much more time constrained), but because it offers more complex abstractions solving generic problems more efficiently (e.g. generics), and since your code is relying on BCL / other libraries that use these abstractions, it benefits from them too. On the other hand, it's hard to expect that cross-compiled code would use them :)

Creator of https://github.com/servicetitan/Stl.Fusion , ex-CTO @ ServiceTitan.com