That sentiment is about 10 years out-of-date. Today, GCC supports modules better than clang/LLVM, and has moved to a minimal C++ coding standard. And time has proven that clang and LLVM are no less a moving target than GCC--it turns out that simply writing things in C++ with OOP doesn't automatically guarantee API compatibility while preserving the ability to hack on the implementation.
GCC can't do runtime retargeting. This is a major drawback because suddenly you need your distro to think about your pet niche target. Suddenly you need your build system to choose the correct linker instead of just being able to use ldd. I'm a big fan of GNU and the GPL, but clang is much better in this regard.
