[skocznymroczny]

I'd say the main determinant is what kind of C++ are you writing and what features of C++ are most important for you. If template metaprogramming is your kind of thing, then you absolutely need to try D, D makes heavy use of template metaprogramming (yes, the lengthy errors you know from C++ make a comeback in D too). If your C++ is more like C with classes, you'll feel right at home in D too.

However, if the most important features of C++ is RAII, shared pointers, unique pointers, move semantics, then you'd probably enjoy Rust more, because it focuses on this kind of memory/resource management techniques.