One factor is time spent on optimizing the compiler or interpreter. In addition to having its own free Python distribution, Intel produces C++ and Fortran compilers. Although it charges for those compilers, I think the main reason it has created them, even though gcc exists, is to increase peformance on its hardware.
- Whether it is compiled or interpreted
- How abstract it is / what 'advanced' features it provides
- The compiler
Can one use the many advanced features of C++ without incurring a speed penalty compared to C?