PC-BSD 10.1 vs. Ubuntu 14.10 vs. Fedora 21 Benchmarks
Clang still (sadly) lacks support for OpenMP so any scientific tests relying upon OpenMP for parallel processing does poorly until LLVM/Clang integrates Intel's OMP work.
The Himeno performance of PC-BSD 10.1 with Clang was relatively the same speed as Ubuntu 14.10 and Fedora 21 with Clang rather than GCC.
Clang continues to do great at offering fast compile times.