I've delved into both GCC and clang to write patches, albeit simple ones. GCC is definitely arcane, but both are pretty impenetrable initially. You can glance at the clang source code and fool yourself into thinking it's easy to hack, but there's no shortage of things to complain about.
Compiler writing is extremely well trodden ground. It shouldn't be surprising that it's fairly easy to go from 0-60 quickly. But it's a marathon, not a sprint. The true test of clang/LLVM is whether it can weather having successive generations of developers hack on it without turning into something that's impossible to work with. GCC has clearly managed this, despite all the moaning, and despite not being sprinkled with magic C++/OOP fairy dust. The past few years have seen tremendously complex features added, and clang/LLVM isn't keeping apace.
And as far as C++11 support, they look neck-and-neck to me: