I can hopefully settle this (as a developer of both). Assuming we stick to x86/x64, nowadays (literally, let's say as of January 2015) GCC and LLVM are within

I can hopefully settle this (as a developer of both). Assuming we stick to x86/x64, nowadays (literally, let's say as of January 2015) GCC and LLVM are within the noise for most people on most code (IE 1-2% of each other). You can certainly find benchmarks were LLVM does badly. Some are important to some people, some aren't. It is harder to find benchmarks where GCC does badly.