Of things I have benchmarked in the past 5 or so years GCC has not been beaten by GCC for any of my workloads or benchmarks. I do mostly things related to 3d graphics and are heavy on the CPU, but what little IO I have done follows this pattern too.
As near as I can tell msvc is strictly inferior except for windows community adoption than gcc/mingw. Of course, benchmark your workload, I could be doing something odd that you are not.