It is not really a myth. While C# and VB.Net both compile to IL, the actual instructions produced are likely to be different because 1. the compilers may have different optimisations and 2. the extra checks that VB.Net does by default e.g. arithmetic overflow. So in many cases the performance will be the same but in some cases C# will be faster. It's also possible VB.Net might be quicker in rare circumstances.
