I'm not sure if this will stoke a flamewar, because I've never seen a discussion here on this (might just be hanging around different articles). Is there any technical reason to prefer clang over gcc other than ideological reasons? I get the modular nature of llvm is useful, but is the android NDK using this feature? Quick google search shows clang lagging gcc in all but one test[0] at least on Intel Broadwell. Again…
I know a number of these issues have been improved/fixed in GCC over the last few years. Outside friendliness to internal tinkering and non-GPL software I'm not sure if one as serious technical superiority. I believe clang is written in C++ instead of C, for whatever that's worth.
GCC has always had a much bigger set of supported platforms and processors.