C# and C++ comparison: Speed issue. Anyone knows how much efficiency is traded off with more features?

Would appreciate if anyone could let me know based on your knowledge the speed trade off for similar programs executed in C++ and C#. I would ume that C++ executes faster than C#....but how much faster (percentage wise) for both CPU intensive computation and GUI apps.. Is it slow and huge like Visual Basic or is it closer to the C/C++ 'hard-core' industrial apps standard speed-wise and size-wise. Thanks...