armclang vs clang

ARM compiler version 6 toolchain uses armclang which is built on LLVM component; clang. In the ARM toolchian, we then have armlink, fromelf and armar. On the LLVM side, we have similar counterparts. So basically one can use LLVM infrastructure and not use ARM toolchain at all for his/her ARM based SoC firmware development. This will be cost effective, but I'm more interested in performance, code size, generated assembly and those kind of differences between the two (armclang and clang). Is there a clear winner here ?