Do you know how the performance of GDScript execution compares to something like Python embedded in an engine where the more costly operations are run in compiled C or C++ code? Or even how the real Python performance in Godot compares to the GDScript performance?

I tried to find this out, but the one "benchmark" I found was somewhat dubious. The Godot documentation claims that GDScript has all sorts of advantages over using other scripting languages that sound qualitatively superior, but it lacks quantitative comparisons.