[cb321]

Rebol/Red is more like Python/Cython - able to be fast but falling back to an interpreter for dynamic things. As such there are probably more "performance footguns" (though any such thing is ultimately subjective based on programmer awareness). Nim feels more like what C++ (or Python) should always have been. Not sure if this helps. It's kind of a "big" question.

[9214]

No, it's actually the other way around: Red and Rebol are interpreted by default, and Red has a bootstrapping AOT compiler capable of bridging it with Red/System (a C-like sub-language), which it turn targets machine code. However, since Red is highly dynamic, compiler cannot preserve semantics across the whole language, so it keeps some parts for the interpreter to process at run-time. And sometimes that's the only option, since code can be generated on-the-fly or pulled over the network: Red is homoiconic and has quite powerful meta-programming facilities on top of that.